Building Equations Given Slope and a Point A-REI.3; F-LE.2; F-CED.2

Table of Contents 38: Guided Practice 39: How Do I Write Equations From Two Points?

EQ: How Do I Write Equations From Two Points? 6/9/2015

PointAlso known as an ordered pair Written (x, y) Slope Rise Run Change in y Change in x Rate of change Represented by “m”

Slope Formula Point – Slope Form y – y 1 = m(x – x 1 ) Slope – Intercept Form y = mx + b

Example 1: Find the equation of the line that passes through (3, 1) and (-4, 15)

y = mx + b 1 = -2(3) + b 1 = -6 + b +6 ________________ 7 = b y = -2x + 7

Guided Practice 1 Find the equation of the line that passes through (2, -5) and (8, 13) y = 3x - 11 Follow Up: What is f(-2) for this function? f(-2) = -17

Guided Practice 2 Find the equation of the line that passes through (4, -1) and (-2, 29) y = -5x + 19 Follow Up: For what x is f(x) = 9? x = 2

Guided Practice 3 Find the equation of the line that passes through (80, 198) and (150, 408) y = 3x – 42 Follow Up: When is the break even point? When x = 14

Questions Which way do you find easier to solve the problem: Slope intercept form or point slope form? Why? What do we know about the points we find the slope with in comparison to the line? Why is knowing the break even point important?

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