设x,y满足2x-y+2>=0,8x-y-4=0,y>=0,若目标函数z=abx+y(a>0,b>0)的最大值是8,则a+b的最小值我已经算出ab=4了 接下去该怎么办QAQ

设Z=X+Y,其中X,Y满足X+2Y>=0,X-Y 设实数x,y满足 x>=0 x-2y>=0 x-y-2 设x,y满足约束条件x>=0 x>=y 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 设变量X,Y满足约束条件{X-Y+3>=0,X+Y>=0,-2 设变量x,y满足约束条件:x-y+3>=0 x+y>=0 -2 设实数X,Y满足2X+Y-2>=0,X-2Y+4>=0,3X-Y 设X,Y满足条件x-y+2>=0,x+y-4>=0,2x-y-5 设实数x,y 满足x²+4y²+2x-4y+2+0 则x+y= 设Z=x+y,其中实数x,y满足不等式x+2y>=0,x-y 设z=x+y,其中实数x,y满足{x+2y>=0,x-y 设实数x,y满足约束条件：x>=2;y>=x;2x+y 设实数x,y满足方程组①x-y-2=0 ③2y-3 设z=2x+y式中变量x,y同时满足x-4y 变量x,y满足x-2y=0,x 设变量x,y满足约束条件 {x-y≥0,x+y≤1,x+2y≥0},则函数Z=2x+y 的最大值? 设变量x,y满足约束条件 {x-y≥0,x+y≤1,x+2y≥0},则函数Z=2x+y 的最大值?