Question

已知a、b、c为三个非负数 ,且a+2b

Answer 1

2b+3c=4-a

4b+2c=3a-6 解得,b=11/8·a-13/4

c=7/2-5/4·a

(1)11/8·a-13/4≥0

∴a≥26/11

7/2-5/4·a≥0

∴ a≤14/5

∴ 26/11≤a≤14/5

(2)S=a+b+c

=a+11/8·a-13/4+7/2-5/4·a

=9/8·a+1/4

由(1),26/11≤a≤14/5

∴32/11≤S≤17/5