# Thread: The scope/limitation of logab X

1. ## The scope/limitation of logab X

loga X = C and logb X = D
i got it up to log ab X = (cd)/(c+d)
the question asked what the scope and/or limitations are. I know that ab and X can't be negatives but i dont know the rest

2. I'm sorry, but I'm not clear on what you're being asked to do...?

Please reply with the full and exact text of the exercise, and the complete instructions. Thank you!

3. Originally Posted by Bzaher
loga X = C and logb X = D
i got it up to log ab X = (cd)/(c+d)
the question asked what the scope and/or limitations are. I know that ab and X can't be negatives but i dont know the rest
I presume you are asking about restrictions on the base of a logarithm and the domain. "not negative" is not enough. They also cannot be zero. ab and X must be positive.

4. Hello, Bzaher!

$\displaystyle \log_a X \,=\, c,\;\;\log_b X \,=\, d$

i got it up to: .$\displaystyle \log_{ab} X \:=\:\frac{cd}{c+d}$

The question asked what the scope and/or limitations are.
The scope and limitations of what?

Here are the restrictions: .$\displaystyle \begin{Bmatrix}X \:>\:0 \\ a \,>\,0,\;a\,\neq\,1 \\ b\,>\,0,\;b\,\neq\,1 \\ c+d\,\neq\,0\end{Bmatrix}$