AlgebraLab

Algebra II Recipe: Writing Equations of Lines

By G Redden

A. Writing Equations into Slope-Intercept Form Given the Slope and Y-Intercept
  1. Use y = mx + b.
  2. Substitute the slope value in place of "m".
  3. Substitute the y-intercept value in place of "b".
1.
Write an equation into y = mx + b given the following information:
m = -¾ and b = 7/3
2.
Write an equation into y = mx + b given the following information:
m = 5 and b = -¼
B. Writing Equations into Slope-Intercept Given the Slope and some Point on the Line
  1. Use point-slope form: y - k = m(x - h), where the given ordered pair is (h,k).
  2. Substitute the slope value in place of "m".
  3. Substitute the "h" coordinate in place of "h".
  4. Substitute the "k" coordinate in place of "k".
  5. Distribute the slope value.
  6. Add or subtract the "k" value on both sides to isolate "y".
3.
Write an equation into y = mx + b given the following information.
(2,3) and m = -½
4.
Write an equation into y = mx + b given the following information.
(-3,4) and m = 2/3
C. Writing Equations into Slope-Intercept Given Two Points on the Line
  1. Find the slope by using the given points and the formula for finding slope. m = (y2 - y1)/(x2 - x1)
  2. Use point-slope form: y - k = m(x - h).
  3. Substitute the slope value in place of "m".
  4. Choose one of the two given points to substitute in place of "h" and "k".
  5. Distribute the slope value.
  6. Add or subtract the "k" value on both sides to isolate "y".
5.
Write an equation into y = mx + b given the following information.
(-2,-1) and (3,4)
6.
Write an equation into y = mx + b given the following information.
(1,5) and (4,2)