Find f'(x) don't know how to slove this 3) f(x) = log9(2^x + 1) the 9 is subscript
Follow Math Help Forum on Facebook and Google+
Originally Posted by bigton Find f'(x) don't know how to slove this 3) f(x) = log9(2^x + 1) the 9 is subscript $\displaystyle \frac{d}{dx}\bigg[\log_a\left(f(x)\right)\bigg]=\frac{d}{dx}\bigg[\frac{\ln\left(f(x)\right)}{\ln(a)}\bigg]=\frac{f'(x)}{f(x)\ln(a)}$
so what rule is this and do i just sub
Originally Posted by theflyingcow so what rule is this and do i just sub That used many rules. If you have to take the derivative of something in the exact form of $\displaystyle y=\log_{a}f(x)$, then yes you can substitute. But this isn't worth memorizing, I promise you.
so subing into the variables into the equation is the answer
For this problem, yes.
View Tag Cloud