若实数a,b满足ab-4a-b+1=0(a>1),则(a+1)(b+2)的最小值为______.
人气:414 ℃ 时间:2019-10-19 13:53:05
解答
∵ab-4a-b+1═0
∴b=
=4+
∴(a+1)(b+2)=6a+
+3
=6a+
+9
=6(a-1)+
+15
≥27(当且仅当a-1=
即a=2时等号成立)
故答案为27.
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