Question

已知y分之x=5分之3,求x²-2xy+y²分之x²-xy- x-y分之x+y的值

Answer 1

原式=(x²-xy)/(x²-2xy+y²)-(x+y)/(x-y)

=x(x-y)/(x-y)²-(x+y)/(x-y)

=x/(x-y)-(x+y)/(x-y)

=(x-x-y)/(x-y)

=-y/(x-y)

x/y=3/5;

原式=-1/(x/y-1)=-1/(3/5-1)=5/2;

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