Question

The points (-4,2) and (4,r) lie on a line with slope -1. Find the missing cooridnate r

Answer 1

r = -6

Step-by-step explanation:

The slope of a line is defined as

$m = \dfrac{y_2 - y_1}{x_2 - x_1}$

Let $P_1(-4, 2)$ and $P_2(4, r)$. Since m = -1, we can write

$-1 = \dfrac{r - 2}{4 - (-4)} \Rightarrow -1 = \dfrac{r - 2}{8}$

or

$r - 2 = -8 \Rightarrow r = -6$