若log9 5=a,log3 7=b,则log35 9=______.

问题描述:

若log9 5=a,log3 7=b,则log35 9=______.

2/(2a+b)
因为log3 7 = b,所以log9 7 = b/2
所以log 9 35 = log9 (5*7) = log9 5 + log9 7 = a + b/2
所以log35 9 = 1/(log9 35) = 1/ (a+b/2) = 2/(2a+b)