计算:1.(x-1+x/1-x)(2/1+x²-1) 2.(3/a-2+12/a²-4)÷(2/a-2-1/a+2)

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计算:1.(x-1+x/1-x)(2/1+x²-1) 2.(3/a-2+12/a²-4)÷(2/a-2-1/a+2)

1.(x-1+x/1-x)(2/1+x²-1)
=(1-x²-1-x)/(1-x)÷(2-1-x²)/(x²+1)
=-x(x+1)/(1-x)×(x²+1)/(1+x)(1-x)
=-(x²+1)/(1-x)²
2.(3/a-2+12/a²-4)÷(2/a-2-1/a+2)
=(3a+6+12)/(a+2)(a-2)÷(2a+4-a+2)/(a+2)(a-2)
=3