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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). 7-99 HW eTool (Desmos)   Homework Help ✎

1. $f(−1)$

Substitute $−1$ for $x$ and simplify.

$f\left(−1\right) = 3\left(2\right)^{−1}$

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

$\frac{3}{2}$

1. $f(0)$

Refer to part (a).

1. $f(1)$

Refer to part (a).

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

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

$x = 2$

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

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

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

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

Use the eTool below to find the value of each expression in parts (a) through (c).
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