Question

a的四次方减去x的四次方+4ax-4a的平方

Answer 1

a^4 - x^4 + 4ax-4a^2
= (a^2 + x^2)(a^2 - x^2) + 4a(x-a)
= (a^2 + x^2)(a + x)(a - x) - 4a(a-x)
= (a - x) [(a^2 + x^2)(a + x) - 4a]