Warm up Write the equation of a line when given: m = -1 b = ½ 3.

Skills Check

Writing Equations of Lines Day 2

Essential Question What’s the equation of a line given the slope and a point on the line? What’s the equation of a line given two points on the line?

I. How to Write an Equation of a Line Given m and a point on the line. 1. Write down y = mx + b 2. Substitute slope for m and the point for (x, y). Solve for b. Substitute m and b back into the equation.

Write the equation of the line given m and a point Ex 1: m = 2 Point: (2, 3) y = mx + b 3 = 2 (2) + b b = -1 y = 2x – 1

Write the equation of the line given m and a point Ex 2: m = ½ Point: (4, -3) y = mx + b -3 = ½ (4) + b b = -5 y = ½ x – 5

Write the equation of the line given m and a point Ex 3: m = -2 Point: (-5, 3) y = mx + b 3 = -2 (-5) + b b = -7 y = -2 x – 7

Write the equation of the line given m and a point Ex 4: m = 4 Point: (1, 4) y = 4x

y = ½ x – 1.5 Ex 5: m = ½ Point: (-1, -2) Write the equation of the line given m and a point Ex 5: m = ½ Point: (-1, -2) y = ½ x – 1.5

Write the equation of the line given m and a point Ex 6: m = und Point: (3, 6) X=3

IV. How to Write an Equation of a Line Given TWO points Write down y = mx + b. Use the slope formula to find m. Pick one of the ordered pairs & substitute slope for m and the point (x, y). Solve for b. Substitute m and b into the equation.

Equation of a Line - Given 2 points Ex: 7 (2, 3) and (4, 5) y = mx + b 3 = 1(2) + b b = 1 y = x + 1

Equation of a Line - Given 2 points Ex: 8 (2, 3) and (-4, 15) y = mx + b 3 = -2(2) + b b = 7 y = -2x + 7

Equation of a Line - Given 2 points Ex: 9 (2, 2) and (0, 4) y = mx + b 2 = -1(2) + b b = 4 y = -x + 4

Equation of a Line - Given 2 points Ex: 10 (2, 3) and (1, 4) y = -x + 5

Equation of a Line - Given 2 points Ex: 11 (4, 5) and (5, 2) y = -3x + 17

Equation of a Line - Given 2 points Ex: 12 (5, -3) and (7, 11) y = 7x -38

Front of Worksheet Only do #6-10 Classwork Front of Worksheet Only do #6-10

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