WAEC 2021 · Paper 1 · Q41

Coordinate geometry

Let $\overline{XY}$ be a line segment with $X(-8, -12)$ and $Y(p, q)$ . If the midpoint of $\overline{XY}$ is $(-4, -2)$ , find the coordinates of $Y$ .

Worked solution (try it first)

The midpoint is the average of the ends, so each coordinate of $Y$ is twice the midpoint's minus $X$ 's.
$p = 2(-4) - (-8) = -8 + 8 = 0$ .
$q = 2(-2) - (-12) = -4 + 12 = 8$ .
So $Y = (0, 8)$ , option B.

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