Question

factorise
$( {x}^{2} - 3x) {}^{2} - 8( {x}^{2} - 3x) - 20$

Answer 1

Let x2 - 3x = t

t2- 8t - 20=0

t2 -10t + 2t - 20= 0

(t+2)(t-10)= 0
So, answer is
(x2-3x+2)(x2-3x-10)