已知(x-1)^2+(y-2)^2=0,求1/xy+1/(x+1)(y+1)+1/(x+2)(y+2)+……+1/(x+1989)(y+1989）的值

已知x,y满足约束条件：x-y+1>=0,x+y-2>=0,x 已知(x+y)^2-2x+2y+1=0,则(x+y)^999= 已知集合A={(x,y)|2x-y+2>=0,x-2y+1 x>0 y>0已知x+2y=1求 1/x+y/1最小值 已知x>y>0,xy=1,求x^2+y^2/x-y的最小值. 已知x+y=1,x>0,y>0,则2x+y/xy等于 已知x>0,y>0,2/x+5/y=1,求x+y最小值 已知（x+y)²-2（x+y）+1=0,则x+y=? 已知|2x-3y|+|3x-y-1|=0,求x,y的值. 已知|x-2y+11+1x+y-5|=0项X-Y的值 已知x>0,Y>0,如何证x^2/y+y^2/x>=x+y 已知M={(x,y)|y=-x^2+mx-1},N={(x,y)|y=-x+3,0 已知实数x,y满足x²+y²-xy+2x-y+1=0 求x y 已知X,Y满足|X-Y-1|+（X+Y-3)^2=0求X,Y的值 已知x^2+y^2-8x+12y+52=0 ,求1/2x-1/x-y(x-y/2x-x^2+y^2) 已知x^2+y^2-8x+12y+52=0 ,求1/2x-1/x-y(x-y/2x-x^2+y^2) 已知(2x+1)*2+y*2+2y+1=0 求{(x*2+y*2)-(x-y)*2+2y(x-y)}/(2y) 已知实数x,y满足x-ay-1>=0,2x+y>=0,x