WAEC 2020 · Paper 1 · Q50

If $(x + 2)$ is a factor of $x^2 + px - 10$ , find the value of $p$ .

Worked solution (try it first)

By the factor theorem, $x + 2$ is a factor, so the expression is 0 at $x = -2$ .
$(-2)^2 + p(-2) - 10 = 0$ , so $4 - 2p - 10 = 0$ and $-2p = 6$ .
So $p = -3$ , option B.