If $f(x)=3(2)^x$, find the value of the expressions in parts (a) through (c) below. Then complete parts (d) through (f).   

4. What value of $x$ gives $f\left(x\right) = 12$?

   Hint (d):

   Substitute $12$ for $f\left(x\right)$ and solve for $x$.

   Answer (d):

   $x = 2$

5. Where does the graph of this function cross the $x$-axis? The $y$-axis?

   Hint (e):

   A function crosses the $x$-axis at $y = 0$, and a function crosses the $y$-axis at $x = 0$.

6. If $g\left(x\right)=\frac{1}{3x}$, find $f(x)·g(x)$.

   Hint (f):

   $\text{Substitute }3(2)^{x}\text{ for }f(x)\text{ and }\frac{1}{3x}\text{ for }g(x).$