题目内容
设
满足约束条件
,若目标函数z=ax+by(a>0,b>0)的最大值为8,则ab的最大值为( )
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A.4 | B.5 | C.7 | D.8 |
A
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如图为满足条件的可行域
因为a>0,b>0,所以在点(1,4)处,目标函数z=ax+by有最大值z=a+4b
∴a+4b=8
∵ab=
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等号当且仅当a=4b,即a=4,b=1时成立
ab的最大值为4.
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题目内容
A.4 | B.5 | C.7 | D.8 |