1.已知1/x+1/y=5,则分式/的值为:2.已知x/=1/3,试求x^2/的值:

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1.已知1/x+1/y=5,则分式/的值为:2.已知x/=1/3,试求x^2/的值:
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1.已知1/x+1/y=5,则分式/的值为:2.已知x/=1/3,试求x^2/的值:
1.已知1/x+1/y=5,则分式/的值为:
2.已知x/=1/3,试求x^2/的值:

1.已知1/x+1/y=5,则分式/的值为:2.已知x/=1/3,试求x^2/的值:
1/x+1/y=5
[x+y]/xy=5
x+y=5xy
/
=[2(x+y)-3xy]/[5xy+2xy]
=[2*5xy-3xy]/[7xy]
=7xy/7xy
=1
x/[x^2+x+1]=1/3
[x^2+x+1]/x=3
x+1/x+1=3
x+1/x=2
[x^4+x^2+1]/x^2=x^2+1/x^2+1=[x+1/x]^2-2+1=2*2-1=3
所以:x^2/[x^4+x^2+1]=1/3