Question

Expand completely using the Binomial Theorem
(3y - x)^4

Answer 1

In standard form it is x^4 - 12x^3y + 54x^2y^2 - 108x y^3 + 81y^4.

Explanation:

(3y)^4 + 4C1(3y)^3(-x) + 4C2(3y)^2(-x)^2 + 4C3(3y)(-x)^3 + (-x)^4

= 81y^4 - 108y^3x + 54y^2x^2 - 12yx^3 + x^4