### Home > GB8I > Chapter 8 Unit 9 > Lesson INT1: 8.2.3 > Problem8-123

8-123.

If $f(x) = 3(2)^x$, evaluate the expressions in parts (a) through (c) below. Then complete parts (d) and (e).

1. $f ( - 1 )$

Substitute $−1$ for $x$ and simplify.

$f(−1) = 3(2)^{−1}$

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

$\frac{3}{2}$

1. $f ( 0 )$

Refer to part (a).

1. $f ( 1 )$

Refer to part (a).

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

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

$x = 2$

1. Where does the graph of this function cross the $x$axis? The $y$‑axis? Use this information to sketch the graph.

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

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: Int1 8-123 HW eTool.