设a,b∈R+,a+2b=3,则1/a+1/b最小值是_.

问题描述:

设a,b∈R+,a+2b=3,则

1
a
+
1
b
最小值是______.

1
a
+
1
b
=
1
3
(a+2b)(
1
a
+
1
b
)=
1
3
(3+
2b
a
+
a
b

1
3
×2
2
+1

1
a
+
1
b
最小值是1+
2
2
3

故答案为:1+
2
2
3