Question 173578: Log(2x+1)+log(x-1)=log9
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Log(2x+1)+log(x-1)=log9
log[(2x+1)(x-1)] = log9
(2x+1)(x-1) = 9
2x^2 - x -1 = 9
2x^2 - x - 10 = 0
2x^2 -5x + 4x - 10 = 0
x(2x-5) + 2(2x-5) = 0
(2x-5)(x+2) = 0
Realistic answer:
x = 5/2
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Comment: x=-2 is extraneous because it would make log(x+1) = log(-1)
which has no meaning.
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Cheers,
Stan H.
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