(a^3 - 6a)^2= a^6 - 12a^4 + 36a^2
(a - x)^2(x + a)^2= (a^2 - 2ax + x^2)(x^2 + 2ax + a^2)= a^2x^2 + 2a^3x - 2a^3x - 4a^2x^2 + x^4 + 2a^2x^2 + 2ax^3 + 4a^2x + a^4= x^4 + 2ax^3 + a^2x^2 + 4a^2x + a^4.
(a^3 - 6a)^2
= a^6 - 12a^4 + 36a^2
(a - x)^2(x + a)^2
= (a^2 - 2ax + x^2)(x^2 + 2ax + a^2)
= a^2x^2 + 2a^3x - 2a^3x - 4a^2x^2 + x^4 + 2a^2x^2 + 2ax^3 + 4a^2x + a^4
= x^4 + 2ax^3 + a^2x^2 + 4a^2x + a^4.