初一计算与因式分解：①(3a-b)(a+b)(a-b)² ②2(x+2)(x-2)-(x+1)² ③

①(3a-b)(a+b)(a-b)² =(3a²+3ab-ab-b²)(a²-2ab+b²)3 4
=(3a²+2ab-b²)(a²-2ab+b²)
=3a4-6a3b+3a²b²+2a3b-4a²b²+2a3b-a²b²+2ab3-b4
=3a4-2a3b-2a²b²+2ab3-b4.
②2(x+2)(x-2)-(x+1)²=2(x²-4)-(x²+2x+1)
=2x²-8-x²-2x-1
=x²-2x-9.
③x²(x-y)+(y-x)=(x-y)(x²-1)
=(x-y)(x+1)(x-1).
④x²-y²-x+y =(x+y)(x-y)-x+y
=(x+y)(x-y)-(x-y)
=(x-y)(x+y-1).
⑤3a³-6a²+3a=3a(a²-2a+1)
=3a(a-1)².

③（x-y）+（y-x）=（x-y）-（x-y）=0④x-y-x+y=（x-x）-（y-y）=0⑤3a-6a+3a=3a×（1-2+1）=3a×0=0 ⊙﹏⊙b汗