Question

(6,2),(9,r),m=-1 find the value of r

Answer 1

The formula of a slope:

`m=(y_2-y_1)/(x_2-x_1)`

We have the points (6, 2) and (9, r), the slope m = -1. Substitute:

`-1=(r-2)/(9-6)\\\\-1=(r-2)/(3)\qquad\text{multiply both sides by 3}\\\\-3=r-2\qquad\text{add 2 to both sides}\\\\\boxed{r=-1}`