Posted by Anonymous on Tuesday, May 18, 2010 at 5:21pm.
How to solve
Log (9x+5) - Log ((x^2)-1) = 1/2
(The 16 is from the logarithmic function : b) (y=log x)
Could anyone post the answer to this?
16 is supposed to be next to Log(16) but lower. This is for both the Logs in the equation.
Re: Algebra II - Reiny, Tuesday, May 18, 2010 at 5:33pm
So we are looking at
log16 (9x+5) - log16</sub (x^2 - 1) = 1/2
log16</sub [(9x+5)/(x^2-1)] = 1/2
(9x+5)/(x^2-1) = 16^(1/2)
(9x+5)/(x^2-1) = 4
4x^2 - 4 = 9x + 5
4x^2 - 9x - 9 = 0
(x-3)(4x + 3) = 0
x = 3 or x = -3/4
but when x = -3/4, the first log term is undefined (we can't take a log of a negative)
so x = 3
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