-4x³y+4x²y²+xy³
16(a-b)²-9 (a+b)²
4x³y+4x²y²+xy³
=xy(4x²+4xy+y²)
=xy(2x+y)²
=[4(a-b)-3(a+b)][4(a-b)+3(a+b)]
=(a-7b)(7a-b)
1:=-xy(4x^2-4xy+y^2)
=-xy(2x-y)^2