1 .a三次方+ab²-2a²b 2.4-12（x-y）+9（x-y）²

a三次方+ab²-2a²b
=a(a^2+b^2-2ab)
=a(a^2-2ab+b^2)
=a(a-b)^2
4-12（x-y）+9（x-y）²
=2^2-2*2*3(x-y)+(3(x-y))^2
=(2-3(x-y))^2
=(2-3x+3y)^2
=(3y-3x+2)^2还有三题 1. （x²+y²）²-4x²y²2.（x²-6）²-6（x²-6）+9 3. （x-1）（x-3）+1（x²+y²）²-4x²y² =x^4+2x^2y^2+y^4-4x^2y^2=x^4-2x^2y^2+y^4=(x^2-y^2)^2=(x+y)^2(x-y)^2 （x²-6）²-6（x²-6）+9=(x^2-6)-2*(x^2-6)*3+3^2=((x^2-6)-3)^2=(x^2-6-3)^2=(x^2-9)^2=(x+3)^2(x-3)^2 （x-1）（x-3）+1=x^2-3x-x+3+1=x^2-4x+4=(x-2)^2