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5(x-y)³-3(x-y)²+7(x-y)-5(x-y)³+(x-y)²-5(

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5(x-y)³-3(x-y)²+7(x-y)-5(x-y)³+(x-y)²-5(x-y),其中,x-y=1/3.
5(x-y)³-3(x-y)²+7(x-y)-5(x-y)³+(x-y)²-5(x-y),其中,x-y=1/3
先化简,再求值;
解5(x-y)³-3(x-y)²+7(x-y)-5(x-y)³+(x-y)²-5(x-y)
=5(x-y)³-5(x-y)³-3(x-y)²+(x-y)²+7(x-y)-5(x-y)
=-2(x-y)²+2(x-y)
=-2(x-y)((x-y)-1)
=-2(1/3)(1/3-1)
=4/9