Monday
April 21, 2014

Homework Help: Maths

Posted by anonymous on Tuesday, June 8, 2010 at 6:22pm.

I got this question, and found what I believe to be the solution, but want it confirmed.

I started with:
log[base5](2x+1) + log[base5](x-1) = 1

And used the product law:
log[base5]((2x+1)(x-1)) = 1
log[base5](2x^2-x-1) = 1

Then I changed to exponential form:
5^1 = 2x^2-x-1
5 = 2x^2-x-1
5-5 = 2x^2-x-1-5
0 = 2x^2-x-6

Then, to find x I used the quadratic formula, ending up with:

x = (1 [+ or -] 5) / 4

The second value of x, -1, was inadmissable, so my final value for x was 3/2.

Is that correct?

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