3-x/2x-4÷（x+2 - 5/x-2)

(3-x)/(2x-4)÷（x+2 - 5/x-2)
=(3-x)/2(x-2)·( (x²-9)/(x-2))
=-1/2(x+3)
(1/(x+1) + 1/(x-1))÷ x/(x+1)
=2x/(x²-1) *(x+1)/x
=2/(x-1)
1/(x+1) - (x+3)/(x²-1) ·( x²-2x+1)/(x²+4x+3)
=-4/(x²-1)·(x+1)/(x+3)
=-4/(x-1)(x+3)
=-4/(x²+2x-3)
（1/x - 1/2)÷（1- x²+4/4x ）
=(2-X)/2x ÷ ( x-x^3+1)/x
=(2-x)/2( x-x^3+1)