1、(a+b+3a)(a+b-3a)=(4a+b)(b-2a)2、-xy(-4xy+4x²y1)=-xy(4x²y²-4xy++1)=-xy(2xy-1)²3、3x^(n+1)(x²-9)=3x^(n+1)(x+3)(x-3)注:3x^(n+1)表示3乘以x的n+1次方