3y+2z=3+x
3y+z=4-3x
相减
z=-1+4x>=0
x>=1/4
y=(4-3x-z)/3=(5-7x)/3>=0
5-7x>=0
x<=5/7
所以1/4<=x<=5/7
w=3x-3(5-7x)/3+4(-1+4x)
=3x-5+7x-4+16x
=26x-9
1/4<=x<=5/7
13/2<=26x<=130/7
13/2-9<=26x-9<=130/7-9
所以w最小=13/2-9=-5/2
最大=130/7-9=67/7