Question

求答案 急

Answer 1

(x³-4xy²) / (x³-4x²y+4xy²)
=[x(x²-4y²)] / [x (x²-4xy+4y²)]
= [(x+2y)*(x-2y)] / (x-2y)²
= (x+2y) / (x-2y)

3x/(x-2)= [3x*(x+2)] / [(x-2)*(x+2)] = (3x²+6x) / (x²-4)
x/(x+2)= [ x*(x-2)] / [(x-2)*(x+2)] = ( x²-2x) / (x²-4)

3x/(2x-2y) = [3x*(x+y)] / [2*(x²-y²)] = (3x²+3xy) / (2x²-2y²)
xy /(x²-y²) = 2xy / (2x²-2y²)

整体代入
1。 x²+1/x²=[ x²+2+(1/x²) ]-2
=(x+1/x)²-2
=2²-2=2
2。 由于x² +1= 4x
x+1/x=4 (因为x≠0，上面等式两边同除x)
x^4+1/x^4=[ x²+(1/x²) ]² -2
=[ (x+1/x)² -2]² -2
= 194
3。 x-y-4xy=0
(2x+3xy-2y) / (x-2xy-y)
=[2*(x-y-4xy)+11xy] / [(x-y-4xy)+2xy]
=11xy/(2xy)
=11/2
4. 1/x - 1/y = 3
x-y=-3xy
(2x+3xy-2y) /(x-2xy-y)
= [2*(-3xy) +3xy] / (-3xy-2xy)
= -3/5