Question

若X Y 满足X+2Y小于等于4,X -Y小于等于1,X + 2大于等于零,则Z = 3X - Y 的最大值?

Answer 1

x+2≥0 x≥-2
x-y≤1 x≤y+1
-2≤x≤y+1
y+1≥-2
y≥-3
x+2y≤4
-2+2y≤x+2y≤y+1+2y≤4
x取最大值y+1,x+2y≤4成立
3y+1≤4
y≤1
-3≤y≤1
z=3x-y
-2-y≤z≤3(y+1)-y=2y+3
z≤2+3=5
z的最大值为5.