Question

设2a=5b=m，且[1/a+1b＝2，则m=（　　）

Answer 1

2^a=m ====>>> log(2)m=a　===>>>> 1/a=log(m)2

5^b=m====>>> log(5)m=b ===>>>> 1/b=log(m)5

1/a＋1/b=2 ====>>>> log(m)2＋log(m)5=2 =====>>>> log(m)10=2 ===>>>> m²=10===>>>>m=√10