已知x分之1加y分之1等于5,求x加2xy加y分之2x减3xy加2y的值
2016-03-02
展开全部
1/x+1/y=5
(2x-3xy+2y)/(x+2xy+y)
分子分母同除以xy得:
= (2/x-3+2/y) / (1/x+2+1/y)
= {2(1/x+1/y)-3} / {(1/x+1/y)+2}
= {2*5-3} / {5+2}
= 7/7
= 1
(2x-3xy+2y)/(x+2xy+y)
分子分母同除以xy得:
= (2/x-3+2/y) / (1/x+2+1/y)
= {2(1/x+1/y)-3} / {(1/x+1/y)+2}
= {2*5-3} / {5+2}
= 7/7
= 1
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