已知X+Y=3,XY=-1,求2(X-Y)^4-9 - 知识问答

已知X+Y=3,XY=-1,求2(X-Y)^4-9(X-Y)^2+12XY

4个回答

X+Y=3
(x+y)^2=9
(x-y)^2+4xy=9
(x-y)^2=9-4(-1)=13
2(X-Y)^4-9(X-Y)^2+12XY
=2*13^2-9*13+12(-1)
=338-117-12
=209

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