1 .a三次方+ab²-2a²b 2.4-12（x-y）+9（x-y）²

1 .a三次方+ab²-2a²b 2.4-12（x-y）+9（x-y）²
1 .a三次方+ab²-2a²b 2.4-12（x-y）+9（x-y）²

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

1 .a三次方+ab²-2a²b
=a(a+b^2-2ab)
=a(a-b)^2
2. 4-12（x-y）+9（x-y）²
=(3(x-y)-2)^2
=(3x-3y-2)^2

1 .a三次方+ab²-2a²b=a(a^2+b^2-2ab)=a(a-b)^2
2. 4-12（x-y）+9（x-y）²=(3x-3y-2)^2

1 .a三次方+ab²-2a²b
=a(a²+b²-2ab)
=a(a-b)²
2. 4-12（x-y）+9（x-y）²
=[3(x-y)-2]²
=(3x-3y-2)²