How do you write an equation in slope-intercept form for a line containing (9,-3) and (5, 5)?

2 Answers
Jun 7, 2017

y=-2x+15

Explanation:

The general form of a linear equation is y=mx+c where m is the gradient (slope) and (0,c) is the y-intercept.

m=(y_2-y_1)/(x_2-x_1) for a line containing (x_1,y_1) and (x_2,y_2).

For (9,-3) and (5,5),
m=(5-(-3))/(5-9)
m=-2

Therefore, y=-2x+c. To find c, substitute (5,5) into this equation.
5=-2(5)+c
c=5+10
c=15

Substitute c value back into equation,
y=-2x+15

Jun 7, 2017

y=-2x+15

Explanation:

We first begin with finding out the slope using the slope formula, which

is (y_2-y_1)/(x_2-x_1). Plug in our points (5-(-3))/(5-9)=-8/2=-2. This is our slope now we use the point slope formula y-y_1=m(x-x_1).

You can pick any of the two points, m is our slope which is -2.

y-5=-2(x-5) go ahead and solve.

You should arrive to the answer of y=-2x+15.

When you do (y_2-y_1)/(x_2-x_1) it doesn't matter which point is your (y_2,x_2) or (y_1,x_1).