5-4 Writing Equations in Slope-Intercept Form Objectives Students will be able to: Write linear equations in slope-intercept form Model real world data with an equation in slope-intercept form

The slope-intercept equation is not only useful for graphing lines, but also for writing equations of lines. You can write linear equations being given a variety of information.

Example 1: Write an equation of a line with the given slope and y-intercept. Slope 5, y-intercept -3 Slope -3, y-intercept 5

Another situation in which you can write a linear equation is if you are given the slope of the line and an ordered pair that the line passes through. Steps Substitute the slope, x value of the ordered pair, and y value of the ordered pair into the slope-intercept equation. Solve for the y-intercept (b). Substitute the slope and y-intercept back into the slope-intercept equation.

Example 2: Write an equation of the line that passes through each point with the given slope. a) (1, 5), m=2 b)

Try these. c) d)

Sometimes, you may not be given the slope Sometimes, you may not be given the slope. Instead you will be given two ordered pairs. In situations such as this, the first thing you need to do is find the slope of the line. After you have the slope, pick one ordered pair, and follow the same process as when you are given the slope and one ordered pair. Note: It does not matter which ordered pair you choose. If your arithmetic is correct, you will end up with the same equation.

Example 3: Write an equation of the line that passes through each pair of points. a) (5, 1) and (8, -2)

b) (-3, -4) and (-2, -8)

Try these. c) (1, 2) and (3, -2) d) (1, 0) and (0, 2)