Hi,

Can someone please tell me how to solve the attached logarithmic problem ? the answer should be 5.

Attached is also my working.

Thanks

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- Nov 11th 2012, 11:10 AM #1

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- Nov 11th 2012, 11:27 AM #2
## Re: Logarithmic problem

log(x^2-5)-log(x) = log(4)

Use the logarithmic law that states that log(a)-log(b) = log(a/b)

log((x^2-5)/x) = log(4) (Here's were your error is in your calculation)

(x^2-5)/x = 4

x^2-5 = 4x

Solving this equation gives the solution x = -1 and x = 5.

But since negative solutions are not defined in the equation log(x) the only solution is x = 5.

- Nov 11th 2012, 11:38 AM #3

- Nov 11th 2012, 11:50 AM #4

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## Re: Logarithmic problem

Thanks for the reply. At skeeter, no the first one was the is the original equation. There is another attachment.

Another problem. The result of the attached problem is 6.66 while on the book it states that the result should be 6.058. What am I doing wrong? Isn't it gust (Ln14.91/(Ln1.5) ??

- Nov 11th 2012, 12:09 PM #5

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- Nov 11th 2012, 12:11 PM #6

- Nov 18th 2012, 07:52 AM #7

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- Nov 18th 2012, 08:19 AM #8
## Re: Logarithmic problem

your binomial coefficient is incomplete ...

$\displaystyle \binom{13}{8} \cdot (3p)^8 \left(\frac{q}{3}\right)^5$

$\displaystyle \frac{13!}{8!(13-8)!} \cdot (3^3 p^8 q^5)$

$\displaystyle 34749p^8q^5$

... next time, start a new problem with a new post. Do not piggy-back onto an older one.

- Nov 18th 2012, 09:11 AM #9

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- Nov 18th 2012, 09:31 AM #10