https://www.youtube.com/watch?v=sULa9Lc4pck

$$log_a(b) $$
Pronounced log *base* a, this function is used to figure out what exponent you need to raise $a$ to to get $b$.

$log_ab = c$ can be rewritten as $a^c = b$.

$$ 5^{log_5^(x+2)}=x+2 $$
By default, $log$ refers to $log_{10}$. $ln$ is shorthand for $log_e$. 

$$ \sqrt{x} = x^{1/2} $$
To get the reciprocal of a value, change the sign of the exponent.
$$ x =