Question

(-55,22) and (4,r) lie on a line with a slope -2 find the missing coordinate r

Answer 1

We have a line with slope m=-2 that pass through the point (-55,22).

We then can write the slope-point equation as:

$\begin{gathered} y-y_0=m(x-x_0) \\ y-22=-2(x+55) \\ y-22=-2x-110 \\ y=-2x-110+22 \\ y=-2x-88 \end{gathered}$

Now we have to find the value of r when for the point in the line (4,r).

We can replace x with 4 and r with y and calculate:

$\begin{gathered} y=-2x-88 \\ r=-2(4)-88 \\ r=-8-88 \\ r=-96 \end{gathered}$

Answer: r=-96