(1) 1/x-1/y=3,分式(2x+3xy-2y)/(x-2xy-y)=_______

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(1) 1/x-1/y=3,分式(2x+3xy-2y)/(x-2xy-y)=_______
(2) 2的n次方+2的-n次方=k,则4的n次方+4的-n次方=______
(3) 若(2m-n)/n=1/3,则m/n=_______
(4) 1/m+1/n=1/(m+n),则n/m+m/n=_______
(5) x方-5x+1=0,则x的四次方+x的四次方分之一=______
(6) 1/x-1/y=3,则(5x+xy-5y)/x-xy-y=_______
(7) a/(b+c)=b/(a+c)=c/(a+b)=x,则x=_______

1:1/x-1/y=3
(y-x)/xy=3
y-x=3xy
x-y=-3xy
所以(2x+3xy-2y)/(x-2xy-y)
=[2(x-y)+3xy]/[(x-y)-2xy]
=-3xy/-5xy
=3/5
2:K²-2
3:2/3
4:-1
1/m+1/n=1/(m+n)
(m+n)^2=mn
n/m+m/n=(n^2+m^2)/mn
=(n^2+m^2+2mn)-2mn/mn
=[(m+n)^2-2mn]/mn
=(mn-2mn)/mn
=-mn/mn
=-1
5:527
x+1/x=5,
X²+1/X²=23
X4+1/X^4=23*23-2=527
6:7/2
1/X-1/Y=3
y-x=3xy
x-y=-3xy
原式=(5X+XY-5Y)/(X-XY-Y)
=(-15xy+xy)/(-3xy-xy)
=14/4
=7/2
7:1/2 或-1
x(b+c)=a x(b+a)=c x(a+c)=b
则a+b+c=x(b+c)+x(b+a)+x(a+c)
化简得a+b+c=(2b+2a+2c)x
a+b+c=2x(a+b+c)
若a+b+c=0,则b+c=-a.
所以a/b+c=-1
即x=-1.
若a+b+c不等于零,则2x=1.
解得x=1/2

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