Question 1051424
{{{(2x-x^2)^4 = sum((matrix(2,1,4,k))*(2x)^(4-k)*(-x^2)^k, k = 0,4)}}}

= {{{sum((matrix(2,1,4,k))*2^(4-k)*x^(4-k)*(-1)^k*x^(2k), k = 0,4)}}}

= {{{sum((-1)^k*(matrix(2,1,4,k))*2^(4-k)*x^(4+k), k = 0,4)}}}


Alternately,

{{{(2x-x^2)^4 = (x(2-x))^4 = x^4*(2-x)^4}}}, expand {{{(2-x)^4}}}, and multiply with {{{x^4}}} afterwards.