化简（a²-2ab)-(3a²+3ab)=( )分解因式 ab-a+b-1=(

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（a²-2ab)-(3a²+3ab)
=a²-2ab-3a²-3ab
=-2a²-5ab
=-a(2a+5b)
ab-a+b-1
=a(b-1)+(b-1)
=(a+1)(b-1)
2xy-x²-y²+1
=-(x²-2xy+y²)+1
=-(x-y)²+1
=-[(x-y)²-1]
=-(x-y+1)(x-y-1)
======以下答案可供参考======
供参考答案1:
（a²-2ab)-(3a²+3ab)=a²-3a²-2ab-3ab=-2a²-5ab=-a(2a=5b)
ab-a+b-1
=a(b-1)+(b-1)=(a+1)(b-1)2xy-x²-y²+1=1-(x+y)^2=(1-x-y)(1+x+y)
供参考答案2:
1、原式=a²-2ab-3a²-3ab
=-2a²-5ab
=-a(2a+5b)
2、原式=(ab-a)+(b-1)
=a(b-1)+(b-1)
=(b-1)(a+1)
3 原式=1-(x²-2xy+y²)
=1²-(x-y)²
=(1+x+y)(1-x+y)