Question

which logarithmic function can be used to approximate the value of y in the equation 4^y=5?

Answer 1

From the definition of logarithm, we know that:

$a^y=b\quad\iff\quad y=\log_ab\qquad\quad \,\text{when }a,b\ \textgreater \ 0\,\,\text{ and }\,\,a\neq1$

In this case $a=4$ and $b=5$ so:

$\boxed{y=\log_45}$