问题描述: 实数x,y满足x>=y>=1和2xx-xy-5x+y+4=0,则x+y=? 1个回答 分类:数学 2014-11-19 问题解答: 我来补答 2X^2 -XY-5X+Y+4 =X^2+X(X-Y)-4X-X+Y+4 =(X-2)^2+(X-1)(X-Y)=0 x≥y≥1(x-2)^2>=0,x-1>=0,x-y>=0,即(x-1)(x-y)>=0两项都非负,故均为0.x-2=0,(x-1)(x-y)=0 即X=2 Y=2 X+Y=4 展开全文阅读