已知x-y除以x+y=3,求代数式x+y分之2(x-y)-3(x-y)分之x+y的值.

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已知x-y除以x+y=3,求代数式x+y分之2(x-y)-3(x-y)分之x+y的值.
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已知x-y除以x+y=3,求代数式x+y分之2(x-y)-3(x-y)分之x+y的值.
已知x-y除以x+y=3,求代数式x+y分之2(x-y)-3(x-y)分之x+y的值.

已知x-y除以x+y=3,求代数式x+y分之2(x-y)-3(x-y)分之x+y的值.
解原式=2(x-y)/(x+y)-(x+y)/3(x-y)
=6(x-y)(x-y)/[3(x+y)(x-y)]-(x+y)x+y)/[3(x-y)(x+y)]
=5(x-y)(x-y)/[(x+y)(x-y)]
=5(x-y)/(x+y)
=5×3=15


原式=2*3-1/3*1/3=53/9

53/9