2. 2.5 Writing Equation of a Line Sept 9, 2013

3. Example 1 Write an Equation Given a Graph Write an equation of the line in slope intercept form. 3 5 y-int(b)

5. Writing Equation of a line given: 1.Substitute the x-coordinate of the point for x and y-coordinate for y and the slope for m in the equation y= mx + b. 2.Solve for b. 3.Now that you have b and m, write the equation of the line in y = mx + b slope and a point

6. Example 2 Write an equation of the line that passes through (4, 2) and has a slope of. 4 1 – = y 3 4 1 – x + y = mx + b 2 = -¼ (4) + b 2 = -1 + b +1 3 = b Substitute 2 for y, 4 for x and -¼ for m Simplify Solve for b

7. Checkpoint Write an equation of the line that passes through the given point and has the given slope. Write your equation in slope-intercept form. ANSWER 5 = 2x2xy+ 7 = 3x3xy+ – 14 = 5x5xy+ ANSWER = y 3 2 x1 – Extra Examples 1. () 31,1, – = m2, 2. () 4,4, 5 – = m3 –, () 42,2, – = m5 3., () 3,3, – 3 – = m 3 2 4.,

8. Find the Equation of the Line Given Two Points ● Calculate the slope of the two points. ● Use one of the 2 points and the slope to substitute into the Slope-intercept equation and solve for b. ● Write your equation in y=mx + b form.

9. Example ● Write the equation of the line that goes through the points (3, 2) and (5, 4). x y x y

10. Extra Example ● Write the equation of the line that goes through the points (4, -1) and (2, -2).

11. Extra Example ● Write the equation of the line that goes through the points (6, -3) and (-4, 2).

12. Homework : 2.5 p.97 #21-23, 25-30, 44-48 Quiz 2.3-2.4 Wednesday