Question 895294
use Pascal's triangle and Binomial theorem to expand the binomial.

{{{(x-2y)^4 = 1(x)^4 + 4(x)^3*(2y) + 6(x)^2*(-2y)^2 + 4(x)(-2y)^2 + 1(-2y)^4}}}
{{{(x-2y)^4 = x^4 - 8x^3y - 12x^2y^2 - 8xy^3 - 16y^4}}}