CPM Homework Help : CCA Problem 7-99

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

$f(−1)$
Hint (a):
Substitute $−1$ for $x$ and simplify.
$f\left(−1\right) = 3\left(2\right)^{−1}$
$=3\cdot\frac{1}{2}$
Answer (a):
$\frac{3}{2}$

$f(0)$
Hint (b):
Refer to part (a).

$f(1)$
Hint (c):
Refer to part (a).

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):
$x = 2$
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 $x = 0$ .
If $g\left(x\right)=\frac{1}{3x}$ , find $f(x)·g(x)$ .
Hint (f):
$\text{Substitute }3(2)^{x}\text{ for }f(x)\text{ and }\frac{1}{3x}\text{ for }g(x).$

Use the eTool below to find the value of each expression in parts (a) through (c).
Click on the link at right for the full eTool version: 7-99 HW eTool