Basic Algebra/Lines (Linear Functions)/Find the Equation of the Line Using Two Points

From Wikibooks, open books for an open world
Jump to navigation Jump to search

Vocabulary[edit | edit source]

Lesson[edit | edit source]

You can find the y intercept(b) of a line by using "point slope" with a pair of cordinates.

-Find the slope (y2 - y1) / (x2 - x1) -Use one of the coordinates (points) and use this formula: y-y1=m(x-x1) -Then you end up with y=mx+b

Example Problems[edit | edit source]

Find the y-intercept of the following coordinates:

(2,1) (3,-7)

(1,3) (3,4)

(0,2) Example 1:

First find the slope m of between the two points:

m = (y-y1) / (x-x1)

m = (6-2) / (3-5)

m = -2

We know that the equation has the form y = mx + b, and we also know that this function passes both of the points, so let's use point #1 to find b:

point #1 (2,1)

2 = m(5) + b

2 = (-2)(5) + b

b = 12

Alternatively, we can use point #2 and get to the same result.

The line equation is:

y = -2x + 12

Practice Games[edit | edit source]

Practice Problems[edit | edit source]