Question

Factorise a(a-4)(a²-4a-1)-20

Answer 1

Step-by-step explanation:

(a2 - 4a)(a2-4a-1)-20 =0

a2-4a-1-20=0

a2-(7-3)a-21=0

a2-7a+3a-21=0

a(a-7)+3(a-7)=0

(a+3)(a-7)=0

a-7=0

a=7