Warm Up – August 16, 2017 Find the slope of the line through each pair of points. (0, 2) and (3, 4) (-2, 8) and (4, 2) (3, 3) and (12, -15) Write the following equations in slope-intercept form 4. y – 5 = 3(x + 2) 5. 3x + 4y + 20 = 0 Write an equation for each line. 6. m = -2 through the point (4, 5) 7. m = 4 and y-intercept is (0, -5)
Homework Answers pg. 78-79 8. ‐1 12. ‐1/5 14. ‐4/5 17. y = 3x + 2 20. y = ‐2 22. y = ‐5x + 4; ‐5, (0,4) 26. y=9/2x ‐ 5; 9/2, (0,5) 51. undeined slope; no y‐int. 52. 0; (0,0) 60. 7/5
2.4 More About Linear Equations Learning Target: When given a point and a slope, I can write a linear equation. Key terms: point‐slope form, standard form of a linear equation, parallel lines, perpendicular lines
Key Terms Point‐slope form – the equation of a line in point-slope form through a point (x1, y1) with slope m is y – y1 = m(x – x1). Standard form of a linear equation – Ax + By = C, where A, B, and C are real numbers and A and B are not both zero. Parallel lines – have same slopes Perpendicular lines – slopes are negative reciprocals
Point‐Slope form: y – y1 = m(x – x1)
“I do” Writing an Equation Given a Point and the Slope A line passes through (‐5, 2) with slope 3/5. What is an equation of the line?
“You do” What is an equation of the line through (7, ‐1) with slope ‐3 in point‐slope form? How would you write this line in Slope‐Intercept form?
“I do” Writing an Equation Given Two Points A line passes through (3, 2) and (5, 8). What is an equation of the line in point‐slope form?
“You do” A line passes through (‐5, 0) and (0, 7). What is an equation of the line in point‐slope form? What is the equation of this line in slope-intercept form?
Standard Form: Ax + By = C 1. A and B cannot BOTH be zero 2 Standard Form: Ax + By = C 1. A and B cannot BOTH be zero 2. x and y both have an exponent of 1 3. x and y are not multiplied together 4. x and y do not appear in denominator, exponents, or radical signs
“I do” Writing an Equation in Standard Form What is an equation of the line y = 2x + 4 in standard form? What is an equation of the line y = ¾ x – 5 in standard form? Use integer coefficients.
“You do” What is an equation of the line y = 3x + 5 in standard form?
“I do” Graphing an Equation Using Intercepts What are the intercepts of 3x + 5y = 15? Graph the equation. What are the intercepts of y = 2x + 4? Graph the equation.
“You do” What are the intercepts of 2/3x + 4y = 12? Graph the equation. What are the intercepts of 4x + 8 = 2y? Graph the equation.
“I do” Writing Equations of Parallel and Perpendicular Lines What is the equation of each line in slope‐intercept form? a. the line parallel to y = 6x – 2 through (1, ‐3) b. the line perpendicular to y = ‐4x + 2/3 through (8, 5)
“You do” What is the equation of each line in slope‐intercept form? the line parallel to 4x + 2y = 7 through (4, ‐2) the line perpendicular to y = 2/3 x – 1 through (0, 6)
Homework pg. 86 # 10, 12, 16, 18, 20, 22, 24, 26, 28, 31, 32, 33, 35, 36, 43, 48, 50