Question

So im doing slope intercept from two points, what is the equation of the line through (2,1) and (5,-8). what does y equal?

Answer 1

Use rise over run to determine the slope of the equation.

Rise over run uses the following formula:

y2 - y1 / x2 - x1

Plug in your points' values into this formula.

$\frac{-8 - 1}{5-2} = \frac{-9}{3} = -3$

Use the slope to find the y-intercept of the equation. Take a point on the line, and apply the slope to it to find the y-intercept.

Take the point (2,1) and subtract the x-value so that it equals 0.

$2 - 2 = 0$

Since we moved the point back by 2, we'll multiply our slope by -2, and add the result to the y-value to find our new point.

$(-2 * -3) + 1 = 6 + 1 = 7$

Our new point is now (0,7). Since x = 0, the y-value will be our y-intercept. The y-intercept is 7.

Slope-intercept form uses the following formula:

$y = mx + b$

m is your slope, and b is your y-intercept. We have already found those values, so plug them into the formula.

The following equation is your answer:

$y = -3x + 1$