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Graphing Lines and Linear Inequalities
Equations Drive on The Education Highway
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Linear Equations and Graphing
1. Parts of a Coordinate Plane 2. Slope 3. Slope-intercept Form of a Linear Equation 4. Graphing by x- & y-intercepts.
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Parts of a coordinate plane.
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Click on the correct quadrant numbers. Correct answer = applause.
6 5 Quadrant Quadrant 4 I II III IV I II III IV 3 2 1 -1 Quadrant Quadrant -2 -3 I II III IV I II III IV -4 -5 -6 Lesson Start
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Click on the correct axis names. Correct answer = clapping.
6 5 4 3 2 1 x-axis y-axis -1 -2 -3 -4 -5 -6 x-axis y-axis Lesson Start
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Click on the point for the origin. Correct answer = clapping.
6 5 4 3 2 1 x -1 -2 -3 -4 -5 -6 Lesson Start y
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Click on point (-3, 5). Correct point = applause.
6 5 4 3 2 1 x -1 -2 -3 -4 -5 -6 Lesson Start y
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You chose a line segment instead of a point.
Go back and try again. INCORRECT ANSWER
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INCORRECT ANSWER You chose point (5, -3).
Each ordered pair is in the form (x, y) -- it follows the alphabet in its internal order. You find the x value first, then you find the y value. Where they meet is the point. Go back and try again. INCORRECT ANSWER
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Click on the correct ordered pair for the black point.
6 5 4 3 2 1 x -1 -2 -5/4 (-5, 4) -3 (4, -5) -4/5 -4 -5 -6 Lesson Start y
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You did not choose an ordered pair.
Go back and try again. INCORRECT ANSWER
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INCORRECT ANSWER You chose the ordered pair for the pale green point.
Remember: x comes before y in the alphabet and in an ordered pair. Go back and try again. INCORRECT ANSWER
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Return to Main Menu. Return to Prior Problem. Continue to Next Lesson.
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Slopes 1. What is a slope? 2. Slope formula 3. Types of slopes
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Slope is the slant of a line. Slope = rise change in y’s
What is slope? Slope is the slant of a line. Slope = rise change in y’s run change in x’s Slope is a fraction/integer. Lesson Start
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How to determine the slope when the line goes up.
1. Count the number of units up from the right point to the left point. 5 4 9 1 2 3 4 5 6 7 8 6 3 5 2 4 1 3 x 2 2. Put that number on top of the fraction line. -1 Slope = 6 1 -2 9 -3 -4 3, Count the number of units to the right. 4. Put that number under the fraction line. y Lesson Start
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How to determine the slope when the line goes down.
1. Count the number of units down from right point to left point. 5 4 -1 3 -2 2 -3 1 -4 x 2. Put that number on top of fraction line. -5 -1 Slope = -6 -6 2 1 3 -2 3 -3 -4 3. Count the units to the right. y 4. Put that number under the fraction line. Lesson Start
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Determine the slope of the line shown.
5 4 3 2 1 x -1 -2 -3 -4 -1/3 3/1 y -3/1 1/3 Lesson Start
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The line does not go down.
Go back and try again. INCORRECT ANSWER Lesson Start
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INCORRECT ANSWER The line does not rise 3 units,
then run 1 unit to the right. Go back and try again. INCORRECT ANSWER Lesson Start
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Determine the slope of the line shown.
5 4 3 2 1 x -1 -2 -3 -4 -2/3 3/2 y -3/2 2/3 Lesson Start
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INCORRECT ANSWER The line does not go up. Go back and try again.
Lesson Start
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INCORRECT ANSWER The line does not rise -2 units,
then run 3 units to the right. Go back and try again. INCORRECT ANSWER Lesson Start
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Slope Formula: m = (y1 - y2) (x1 - x2) where m = slope
and (x1, y1), (x2, y2) are points on the line. Lesson Start
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1. Assign values as follows:
Example: Find the slope for a line with points (-3, 4) and (7, -2) on it. 1. Assign values as follows: (x1, y1) = (-3, 4) (x2, y2) = (7, -2) 2. Substitute them into the formula and solve. m = 4 - (-2) = = -3 Lesson Start
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Find the slope of the line with points (5, 6) and (2, 9) on it.
1. (x1, y1) = (5, 6) (2, 9) Lesson Start
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Find the slope of the line with points (5, 6) and (2, 9) on it.
1. (x1, y1) = (5, 6) 2. (x2, y2) = (5, 6) (2, 9) Lesson Start
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Find the slope of the line with points (5, 6) and (2, 9) on it.
1. (x1, y1) = (5, 6) 2. (x2, y2) = (2, 9) 6 + 9 5 + 2 6 - 9 5 - 2 3. m = 5 - 2 6 - 9 5 + 2 6 + 9 Lesson Start
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The slope formula is a case of subtraction
on top and bottom. Go back and try again. INCORRECT ANSWER Lesson Start
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INCORRECT ANSWER You have your x’s and y’s upside down. Remember:
“Y’s guys are always in the skies!” Go back and try again. INCORRECT ANSWER Lesson Start
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INCORRECT ANSWER You have your x’s and y’s upside down.
You are also adding when you need to subtract. Go back and try again. INCORRECT ANSWER Lesson Start
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Find the slope of the line with points (5, 6) and (2, 9) on it.
1. (x1, y1) = (5, 6) 2. (x2, y2) = (2, 9) 3. m = = -3 = -1 Lesson Start
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Find the slope of the line with points (7, 5) and (3, -4) on it. m =
5 - 4 = 1 = 4 5 - (-4) 9 5 - (-4) = 9 5 - (-4) = 9 Lesson Start
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INCORRECT ANSWER You have your x’s and y’s upside down. Remember:
“Y’s guys are always in the skies!” Go back and try again. INCORRECT ANSWER Lesson Start
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INCORRECT ANSWER It is not 5 - 4, it is 5 - (-4).
Go back and try again. INCORRECT ANSWER Lesson Start
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You must start with the y and x from the first point and end with the y and x from the second point.
Go back and try again. INCORRECT ANSWER Lesson Start
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Types of Slopes: 1. Positive and Negative Slopes
2. Special Types of Slopes 3. Determining Types of Slopes by Looking at Graphs of Lines 4. Determining Types of Slopes Algebraically. Lesson Start
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Positive and Negative Slopes.
Type Graph Algebra Positive Up left to right. Positive Fraction SMILE Negative Down left to right Negative Fraction Frown Lesson Start
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2 Special Types of Slopes Type Graphs Algebra
Zero Horizontal Line 0/a, a 0 Why, o y, do I look upon the horizon? Undefined Vertical Line a/0 No Slope Lesson Start
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Determining Types of Slopes by Looking at Graphs of Lines
Lesson Start
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+ - Is the slope of the line positive, negative, zero, or undefined?
5 4 3 2 1 x -1 -2 -3 -4 + - y Lesson Start
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+ - Is the slope of the line positive, negative, zero, or undefined?
5 4 3 2 1 x -1 -2 -3 -4 + - y Lesson Start
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+ - Is the slope of the line positive, negative, zero, or undefined?
5 4 3 2 1 x -1 -2 -3 -4 + - y Lesson Start
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+ - Is the slope of the line positive, negative, zero, or undefined?
5 4 3 2 1 x -1 -2 -3 -4 + - y Lesson Start
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Click on the line with the negative slope.
5 4 3 2 1 x -1 -2 -3 -4 y Lesson Start
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Click on the line with the zero slope.
5 4 3 2 1 x -1 -2 -3 -4 y Lesson Start
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Click on the line with the no slope.
5 4 3 2 1 x -1 -2 -3 -4 y Lesson Start
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Click on the line with the positive slope.
5 4 3 2 1 x -1 -2 -3 -4 y Lesson Start
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Determining Types of Slopes
Algebraically. Lesson Start
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Is the slope of the line with the 2 points listed positive, negative, zero, or undefined?
Points (-3, 5) and (-9, -4) + - Lesson Start
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Is the slope of the line with the 2 points listed positive, negative, zero, or undefined?
Points (3, 5) and (3, -4) + - Lesson Start
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Is the slope of the line with the 2 points listed positive, negative, zero, or undefined?
Points (-3, -5) and (-9, -4) + - Lesson Start
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Is the slope of the line with the 2 points listed positive, negative, zero, or undefined?
Points (-3, -4) and (-9, -4) + - Lesson Start
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Return to Main Menu. Return to Prior Problem. Continue to Next Lesson.
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Slope-intercept Form of a Linear Equation 1. Slope-intercept equation
2. Graphing by slope-intercept 3. Writing slope-intercept equations
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Slope-intercept Form:
y = mx + b where m = slope and b = y-intercept. Lesson Start
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Example: y = -1/2x + 4 -1/2 = m = slope 4 = b = y-intercept Lesson
Start
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Graphing by Slope-intercept
1. Graphing lines with positive/negative slopes. 2. Graphing lines with zero or undefined/no slopes. Lesson Start
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The Slope-intercept Song
You make the last number first. It’s either up or down. Make the slope in 2 numbers, Or you look like a clown. Top one’s up or down, And the bottom’s always right. You’d better do it well, Or you’ll get a fright. (Tune: “Hokey-Pokey”) Lesson Start
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Graph y = -1/2x + 4 4. Draw a line through the 2 points you plotted. 1. Last number is 4, so go up 4 on the y-axis from the origin and plot a point. 2. Slope is already 2 numbers. Top one is -1, so go down 1 from the point you just plotted. 5 4 3 3 2 2 1 1 x -1 3. The bottom number is 2, so go 2 units to the right and plot a point. -2 -3 -4 y Lesson Start
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Graph y = 2x - 3 1 1 2 4. Go 1 unit to the right and plot a point.
1. Last number is -3, so go down 3 units from the origin and plot a point. 2. The slope is only 1 number so put a 1 under the 2. 5 4 3 2 1 x 1 -1 3. Go up 2 from the point you just plotted. 5. Draw a line through the 2 points you plotted. 2 -2 -3 -4 y Lesson Start
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Click on the graph for y = 2/3x - 2
5 4 3 2 1 x -1 -2 -3 -4 y Lesson Start
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The slope is not negative.
Go back and try again. INCORRECT ANSWER Lesson Start
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You graphed the last number on the x-axis instead of the y-axis.
Go back and try again. INCORRECT ANSWER Lesson Start
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INCORRECT ANSWER Top number is 2, and the bottom is 3,
so you do not go up 3 and over 2. Go back and try again. INCORRECT ANSWER Lesson Start
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Click on the graph for y = -4x + 3
5 4 3 2 1 x -1 -2 -3 -4 y Lesson Start
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The slope is not positive.
Go back and try again. INCORRECT ANSWER Lesson Start
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INCORRECT ANSWER The -4 is not the y-intercept,
nor is the 3 the x-intercept. Go back and try again. INCORRECT ANSWER Lesson Start
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The -4 is the slope, not the x-intercept.
Go back and try again. INCORRECT ANSWER Lesson Start
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Line with an undefined slope.
Two Special Graphs: Line with a zero slope And Line with an undefined slope. Lesson Start
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“Why, o y, do I look upon the horizon?”
Line with a zero slope: y = # (no x) graphs as a horizontal line. “Why, o y, do I look upon the horizon?” Lesson Start
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Graph the equation y = 2. x y Lesson Start 5 4 3 2 1
-1 -2 -3 -4 y Lesson Start
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Line with an undefined/no slope: x = # (no y)
graphs as a vertical line. Lesson Start
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Graph the equation x = -4. x y Lesson Start 5 4 3 2 1
-1 -2 -3 -4 y Lesson Start
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Click on the graph for x = 3.
5 4 3 2 1 x -1 -2 -3 -4 y Lesson Start
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You chose the graph for x = -3.
Go back and try again. INCORRECT ANSWER Lesson Start
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The x = # (no y) line does not graph
as a horizontal line. Go back and try again. INCORRECT ANSWER Lesson Start
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Click on the graph for y = -3½.
5 4 3 2 1 x -1 -2 -3 -4 y Lesson Start
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The y = # (no x) line does not graph
as a vertical line. Go back and try again. INCORRECT ANSWER Lesson Start
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You chose the graph for y = 3½.
Go back and try again. INCORRECT ANSWER Lesson Start
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Writing Slope-intercept Equations:
1. When given a slope and the y-intercept. 2. When given a slope and one point on the line. 3. When given 2 points on the line. m = ¾, b = -1 m = -¼, (8, 3) (3, 7), (5, 12) Lesson Start
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Substitute the slope and the y-intercept
Writing a slope-intercept equation when given a slope and the y-intercept. Substitute the slope and the y-intercept for the m and b in the equation. Example: m = ¾, b = -1 y = mx + b Slope-int. equation y = ¾x The new equation Lesson Start
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1. Click on the correct equation for a line with
slope = 5/3 and y-intercept = 2. 5/3y = 2x y = 2x + 5/3 y = 5/3x + 2 y = -5/3x + 2 2. Click on the correct slope and y-intercept pair for y = 7x - 5. m = 7, b = -5 m = -5, b = 7 m = -7, b = 5 m = 1/7, b = -5 Lesson Start
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1. Substitute the x, y, and m in the slope-intercept form.
Writing a slope-intercept equation when given a slope and a point on the line. 1. Substitute the x, y, and m in the slope-intercept form. 2. Solve for b. 3. Substitute the slope and the b in a clean slope-intercept form. Lesson Start
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Example: Write the equation of the line with
slope = -¼ and point (8, 3). y = mx + b 3 = -¼(8) + b 1. Substitute the slope, x, and y in the equation. 2. Solve for b. 3 = -2 + b +2 +2 5 = b 3. Substitute the slope and b in the equation. y = -¼x + 5 Lesson Start
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1. Click on the correct substitution for a line
with slope = 1/3 and point (5, 9). 9y = 5x + 1/3 9 = 1/3x + 5 9 = 1/3(5) + b 5 = 1/3(9) + b 2. Click on the correct equation for a line with slope = -2/3 and point (-6, 4). y = -2/3x - 6 y = -2/3 Y = -2/3x + 4 y = -2/3x Lesson Start
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Writing a slope-intercept equation for a line with 2 points given:
1. Find the slope of the line. 2. Use that slope and the first point to find the y-intercept. 3. Substitute the slope and the y-intercept into the equation. Lesson Start
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Continued on next screen.
Example: Write and equation for a line with points (3, 7) & (5, 12). m = (y1 - y2) (x1 - x2) m = = -5 = 5 1. Find the slope of the line. Continued on next screen. Lesson Start
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Continued on next screen.
Write and equation for a line with points (3, 7) & (5, 12). m = 5/2 y = mx + b 7 = (5/2)(3) + b 2(7) = 2(15/2) + 2b 14 = b -1 = 2b -1/2 = b 2 2 2. Use the slope and the first point to solve for the y-intercept. Continued on next screen. Lesson Start
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Write and equation for a line with points (3, 7) & (5, 12).
m = 5/2, b = -1/2 3. Substitute the slope and the y-intercept for the m and the b in the equation. y = mx + b y = 5/2x - 1/2 Lesson Start
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1. Click on the slope for a line with points (-2, 8) and (7, -5).
3 -9 13 -9 -9 13 13 9 2. Click on the y-intercept for a line with points (-2, 8) and (7, -5). 86 9 -5 86 13 46 9 Lesson Start
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3. Click on the correct equation for a line
with points (3, 7) and (4, 8). y = 3x + 7 y = 3/4x + 8 y = x + 4 y = -x + 4 Lesson Start
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Return to Main Menu. Return to Prior Problem. Continue to Next Lesson.
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Graphing by x- and y-intercepts.
X-intercept: where the line crosses the x-axis. Y-intercept: where the line crosses the y-axis. x-intercept x y-intercept y
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How to graph by x- & y-intercepts:
1. Cover the x term with your index finger and solve the resulting equation for y. 2. Go up or down on the y-axis from the origin that many units and plot a point. 3. Cover the y term with your index finger and solve the resulting equation for x. 4. Go left or right on the x-axis from the origin that many units and plot a point. 5. Draw a line through your points. Lesson Start
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1. Cover the x term and solve for y.
Graph the line for 3x + 2y = 6. 1. Cover the x term and solve for y. 3x + 2y = 6. 2. Go up 3 units on the y-axis. 5. Draw a line through the points plotted. 5 4 3 2 2 y = 3 1 1 x 1 3. Cover the y term and solve for x. 3x + 2y = 6. 4. Go right 2 units on the x-axis. -1 -2 -3 -4 x = 2 y Lesson Start
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1. Click on the correct intercepts for 3x - 4y = 24.
x-int: 8 y-int: 6 x-int: 8 y-int: -6 x-int: 6 y-int: 8 x-int: -6 y-int: 8 Lesson Start
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2. Click on the graph of 3x - 6y = 12.
5 4 3 2 1 x -1 -2 -3 -4 y Lesson Start
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3. Click on the correct equation for the line shown.
5 -9y - 6x = -36 4 4x + 6y = 36 3 2 1 x -1 6y + 4x = 36 -6x - 9y = -36 -2 -3 -4 y Lesson Start
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Return to Main Menu. Return to Prior Problem. Continue to Next Lesson.
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Graphing Linear Inequalities
Type of Line Solving Inequalities Where to Shade
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Inequality Symbol Type of Line > or < Dotted Line Solid Line
How to Determine the Type of Line to Draw Inequality Symbol Type of Line > or < Dotted Line Solid Line
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Choose the type of line for the inequality given.
1. y > 3x - 2 a. Solid b. Dotted 2. y > ¼x - 5 Lesson Start
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Choose the inequality symbol for the line shown.
Lesson Start
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Choose the inequality symbol for the line shown.
Lesson Start
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For Positive, Negative, & Zero Slopes
Where to Shade For Positive, Negative, & Zero Slopes For Undefined or No Slopes
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Where to Shade for Positive, Negative, and Zero Slopes:
The inequality must be in y mx + b format. can be: >, >, <, or <. Lesson Start
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If the inequality is: Shade y > mx + b or Above the line
Below the line Lesson Start
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Graph y > x - 2. 1. Graph the line y = x - 2. x
2. Since y >, shade above the line. y Lesson Start
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Graph y < x - 2. 1. Graph the line y = x - 2. x
2. Since y <, shade below the line. y Lesson Start
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Do you do anything different when the line is dotted rather than solid?
Lesson Start
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Not Really Lesson Start
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Graph y > x - 2. 1. Graph the line
y = x - 2, but make the line dotted. x 2. Since y >, shade above the line. y Lesson Start
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Graph y < x - 2. 1. Graph the line
y = x - 2, but make the line dotted. x 2. Since y <, shade below the line. y Lesson Start
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Graph y > -½x + 3 Type of line: Solid Dotted x y Lesson Start
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Graph y > -½x + 3 Type of line: Solid Dotted x Shade ___ the line.
Above Below Lesson Start
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Graph y > -½x + 3 Type of line: Solid Dotted x Shade ___ the line.
Above Below Lesson Start
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Choose the correct inequality for the graph shown.
y < 1/3 x + 2 y < 1/3 x + 2 x y > 1/3 x + 2 y > 1/3 x + 2 y Lesson Start
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Where to Shade for Undefined or No Slopes:
The inequality must be in x # (no y) format. can be: >, >, <, or <. Lesson Start
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If the inequality is: Shade To the x > # or Right of the line
Left of the line Lesson Start
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Graph x > -2 1. Draw a dotted vertical line at x = -2. x
2. Shade to the right of the line. y Lesson Start
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Graph x < -2. 1. Graph the line X = -2. x
2. Shade to the left of the line. y Lesson Start
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Graph x > 3. Choose type of line. Solid Dotted x y Lesson Start
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Graph x > 3. Choose type of line. Solid Choose where to shade. Left
Right y Lesson Start
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Graph x > 3. Choose type of line. Solid Choose where to shade.
Right y Lesson Start
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Solving Inequalities You use the same algebraic methods as solving equations except when you multiply/divide both sides by the same negative number. In that case, you switch the direction of the inequality symbol. Lesson Start
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Solve -3x - 2y < 12. -3x - 2y < 12 +3x +3x -2y < 3x + 12
y < -3/2 x - 6 > Lesson Start
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Choose the correct inequality. 1. 2x + 5y > -10
Lesson Start
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