If the distance between points (3,y) and (8,7) is 13, then y is equal to __________.
- 5 or -5
- 5 or 19
- 19
- -5 or 19
By trial & error substitution,
Try a.
\[
d = \sqrt{(x_2-x_1)^2 + (y_2-y_1)^2}
\]
\[
13 \stackrel{?}{=} \sqrt{(8-3)^2 + (7-5)^2}
\]
\[
13 \neq 5.38516480713
\]
$\therefore b. \neq 13$
Try c.
\[
d = \sqrt{(x_2-x_1)^2 + (y_2-y_1)^2}
\]
\[
13 \stackrel{?}{=} \sqrt{(8-3)^2 + (7-19)^2}
\]
\[
13 = 13
\]
Try d.
\[
d = \sqrt{(x_2-x_1)^2 + (y_2-y_1)^2}
\]
\[
13 \stackrel{?}{=} \sqrt{(8-3)^2 + [7-(-5)]^2}
\]
\[
13 = 13
\]
$ \therefore \text{d.} \leftarrow \text{answer} $
