WAEC 2019 · Paper 1 · Q13

Solve $4x^2 - 16x + 15 = 0$ .

Worked solution (try it first)

Find two numbers with product $4 \times 15 = 60$ and sum $-16$ : they are $-6$ and $-10$ .
Split and group: $4x^2 - 6x - 10x + 15 = 2x(2x - 3) - 5(2x - 3)$
$= (2x - 3)(2x - 5)$ .
So $x = \frac32 = 1\frac12$ or $x = \frac52 = 2\frac12$ , option B.