WAEC 2023 · Paper 1 · Q9

Find the roots of the equation $3m^2 - 2m - 65 = 0$ .

Worked solution (try it first)

Find two numbers with product $3 \times (-65) = -195$ and sum $-2$ : they are $-15$ and 13.
Split and group: $3m^2 - 15m + 13m - 65 = 3m(m - 5) + 13(m - 5)$
$= (3m + 13)(m - 5)$ .
So $m = 5$ or $m = -\frac{13}{3}$ , option C.