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# ln(5x+6) = 2ln(5x-6) Wrong answer in textbook?? watch

1. So the answer in the back is x=2, I also got this as one of two answers - the other being x=3/5. Any ideas apart from David Rayner and Paul Williams being a pair of pricks?
2. (Original post by G_MItch)
So the answer in the back is x=2, I also got this as one of two answers - the other being x=3/5. Any ideas apart from David Rayner and Paul Williams being a pair of pricks?
Remember, you can't take logs of a negative thing. So x=3/5 is meaningless to ln(5x-6)

Edit: Having thought about it, I guess you could take lns of a negative thing. If ln(ab) = ln(a) + ln(b) then I guess ln(-x) = ln(x) + ln(-1), and because we know e^ipi=-1, then ln(-1) would be ipi. But regardless, that still means x=3/5 wouldn't be an answer
3. Perform steps to make them no longer ln.
4. (Original post by G_MItch)
So the answer in the back is x=2, I also got this as one of two answers - the other being x=3/5. Any ideas apart from David Rayner and Paul Williams being a pair of pricks?
Beautiful.
But yes, it's only x = 2

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Updated: February 28, 2016
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