Question

How to factorise 9x4-x2-12x-36 and a(a-1)-b(b-1)

Answer 1

(1)
(3x^2)^2-(x2+12x+36)
=(3x^2)^2-(x+6)^2
=(3x2+x+6)(3x2-x-6) {a^2 - b^2 = (a+b)(a-b) }
(2)
a²-a-b²+b
a²-b²-(a-b)
(a+b)(a-b)-(a-b)
(a-b)(a+b-1)