已知X+Y=-4,XY=-12,求Y+1/X-1+X+1/Y-1的值看清楚啊……是Y+1/X-1+X+1/Y-1啊……

问题描述:

已知X+Y=-4,XY=-12,求Y+1/X-1+X+1/Y-1的值
看清楚啊……是Y+1/X-1+X+1/Y-1啊……

Y+1/X-1+X+1/Y-1=y²-1+x²-1/[(x-1)(y-1)]=x²+y²-2/[xy-(x+y)+1=
(x+y)²-2xy-2/[xy-(x+y)+1]=(16+24-2)/(-12-(-4)+1)=-38/7