### Home > CCA2 > Chapter B > Lesson B.2.2 > ProblemB-97

B-97.

If $f(x) = 3(2)^x$, find the value of the expressions in parts (a) through (c) below. Then complete parts (d) through (f). B-97 HW eTool (Desmos).

1. $f(-1)$

1. $f(0)$

1. $f(1)$

1. What value of $x$ gives $f(x) = 12$?

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

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

Substitute $-1$ for $x$ and simplify.

$f(−1) = 3(2)^-1$

$=3\cdot\frac{1}{2}$

$\frac{3}{2}$

Refer to part (a).

Refer to part (a).

Substitute $12$ for $f(x)$ and solve for $x$.

$x = 2$

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

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

Use the eTool below to find the value of each expression.
Click the link at right for the full version of the eTool: CCA2 B-97 HW eTool