八下数学分式(1)已知1/x-1/y=5,求分式3x+5xy-3y/x-3xy-y的值(2)已知x+1/x=3,求分式x
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八下数学分式
(1)已知1/x-1/y=5,求分式3x+5xy-3y/x-3xy-y的值
(2)已知x+1/x=3,求分式x^2+1/x^2的值
(1)已知1/x-1/y=5,求分式3x+5xy-3y/x-3xy-y的值
(2)已知x+1/x=3,求分式x^2+1/x^2的值
1)由1/x-1/y=5,得(y-x)/xy=5,
所以y-x=5xy,
即x-y=-5xy
(3x+5xy-3y)/(x-3xy-y)
=[3(x-y)+5xy]/[(x-y)-3xy]
=(-15xy+5xy)/(-5xy-3xy)
=-10/(-8)
=5/4
2)将x+1/x=3平方,
(x+1/x)^2=9,
x^2+2+1/x^2=9
所以x^2+1/x^2=9-2=7
所以y-x=5xy,
即x-y=-5xy
(3x+5xy-3y)/(x-3xy-y)
=[3(x-y)+5xy]/[(x-y)-3xy]
=(-15xy+5xy)/(-5xy-3xy)
=-10/(-8)
=5/4
2)将x+1/x=3平方,
(x+1/x)^2=9,
x^2+2+1/x^2=9
所以x^2+1/x^2=9-2=7
八下数学分式(1)已知1/x-1/y=5,求分式3x+5xy-3y/x-3xy-y的值(2)已知x+1/x=3,求分式x
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