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先化简,再求值:{(xy-2)^2+4xy-4}/(-xy),其中x=1.,y=-1/25
人气:228 ℃ 时间:2020-05-03 16:28:47
解答
{(xy-2)^2+4xy-4}/(-xy)={(xy-2)^2+2(xy-2)+1+2xy-1}/(-xy)={[(xy-2)+1]^2+2xy-1}/(-xy)={(xy-1)^2+2xy-1}/(-xy)={(xy)^2-2xy+1+2xy-1}/(-xy)=(xy)^2/(-xy)=-xy=-1*(-1/25)=1/25
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