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问题: 高一对数问题       83 

解答:

解:log8(3)=p,===> lg3/lg8=p
log3(5)=q, ===> lg5/lg3=p
∴p*q=(lg3/lg8)*(lg5/lg3)
`````=lg5/lg8
`````=lg5/lg(2^3)
`````=lg5/3lg2
`````=lg5/3lg(10/5)
`````=lg5/3(1-lg5)
∴lg5/3(1-lg5)=pq, ===> lg5=3pq(1-lg5),
===> lg5=3pq-3pqlg5, ===> (1+3pq)lg5=3pq,
===> lg5=3pq/(1+3pq)