Answer
$f(x)=2\log x$
Work Step by Step
$f(x)=2\log x$
(the base of the common logarithm is 10.)
Create a table of function values.
For x, select powers of $10$, since $\log 10^{n}=n$
$\left[\begin{array}{lllllll}
x & 1/10 & 1 & \sqrt{10} & 10 & 100 & \\
f(x) & -2 & 0 & 1 & 2 & 4 &
\end{array}\right]$
Plot the points and join with a smooth curve.