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# Logs

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Why bother with a post grad? Are they even worth it? Have your say! 26-10-2016
1. How do they get the answer as that single logarithm? I just cant see it, thanks
2. (Original post by rpnom)
How do they get the answer as that single logarithm? I just cant see it, thanks
You should know that 25 = 5^2.

So ln (25) = ln (5^2) = 2 ln 5.

So -1/6 ln 25 = -2/6 ln 5 = -1/3 ln 5.

Then you add -1/3 ln 5 to 3 ln 5.

That's ln 5 ( 3 - 1/3) = ...

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