y={2,X≥0.-1,X

设变量x y满足约束条件x-y≥-1 x+y≥1 2x-y≤1 z=(x-2y)/(x+y)的最大值 y={2,X≥0.-1,X y={2,X≥0.-1,X x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 已知变量X,Y 满足{X≥1,Y≤2,X-Y≤0.则Z=X+Y 的最小值为 （ ）求图像!X≥1,Y≤2,X-Y≤0 求图像. 已知x+y=a,2x-y=-2a,求[（x/y-y/x)/(x+y)-x(1/x-1/y)]/[(x+1)/y]的值 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 （x-y)(x+y)-(x+y)^2+2y(y-x),其中x=1,y=3. 2y(x+二分之一y)-[(x+y)(x-y)+2y(y+x)],其中|x-1|=2 求y=(x^2)+2x(x≥0) y=-x+2x(x x+2y=2x+y+1=7x-y 求：2x-y? 设x,y满足约束条件x+y>=1,x-y>=-1,2x-y 设x,y满足约束条件x+y>=1,x-y>=-1,2x-y 二元一次方程 ：2(x+y)-(x-y)=3 (x+y)-2(x-y)=1 (3x-y)^2+(3x+y)(3x-y),x=1,y=-2 y=(2x)/x-1化简成用y表示x 2(x+y)-3(x-y)=1 6(x+y)+(x-y)=51 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1