> 数学 >
(2011•琼海一模)设3a=4b=m,且
1
a
+
1
b
=2,则m=(  )
A. 12
B. 2
3

C. 4
3

D. 48
人气:391 ℃ 时间:2019-09-29 03:19:37
解答
由3a=4b=m得,a=
logm3
,b=
logm4

1
a
=
log3m
1
b
=
log4m
,∴
1
a
+
1
b
=
log3m
+
log4m
=
log12m
=2,
∴m2=12,即m=2
3

故选B.
推荐
猜你喜欢
© 2024 79432.Com All Rights Reserved.
电脑版|手机版