WAEC 2021 · Paper 1 · Q21

Find the quadratic equation whose roots are $-2q$ and $5q$ .

Worked solution (try it first)

The sum of the roots is $-2q + 5q = 3q$ .
The product is $(-2q)(5q) = -10q^2$ .
The equation is $x^2 - (\text{sum})x + (\text{product}) = 0$ , which is $x^2 - 3qx - 10q^2 = 0$ , option D.