Question

Solve the following quadratic equation by factorisation.
$x^2-7x-18=0$.

Answer 1

$x^2-7x-18=0$

$x^2-9x+2x-18=0$

$x(x-9)+2x-18=0$

$x(x-a)+2(x-9)=0$

$(x-9)(x+2)=0$

$x=9-2$