Graph f(x)=3^x , f^-1(x) = log base 3 of x

$f (x) = 3^{x}$ , $f^{- 1} (x) = \log_{3} (x)$

Step 1

Exponential functions have a horizontal asymptote. The equation of the horizontal asymptote is $y = 0$ .

Horizontal Asymptote: $y = 0$

Step 2

Graph $f^{- 1} (x) = \log_{3} (x)$ .

Find the asymptotes.

Set the argument of the logarithm equal to zero.

$x = 0$

The vertical asymptote occurs at $x = 0$ .

Vertical Asymptote: $x = 0$

Find the point at $x = 1$ .

Replace the variable $x$ with $1$ in the expression.

$f (1) = \log_{3} (1)$

Simplify the result.

Logarithm base $3$ of $1$ is $0$ .

$f (1) = 0$

The final answer is $0$ .

$0$

Convert $0$ to decimal.

$y = 0$

Find the point at $x = 3$ .

Replace the variable $x$ with $3$ in the expression.

$f (3) = \log_{3} (3)$

Simplify the result.

Logarithm base $3$ of $3$ is $1$ .

$f (3) = 1$

The final answer is $1$ .

$1$

Convert $1$ to decimal.

$y = 1$

Find the point at $x = 9$ .

Replace the variable $x$ with $9$ in the expression.

$f (9) = \log_{3} (9)$

Simplify the result.

Logarithm base $3$ of $9$ is $2$ .

Rewrite as an equation.

$\log_{3} (9) = x$

Rewrite $\log_{3} (9) = x$ in exponential form using the definition of a logarithm. If $x$ and $b$ are positive real numbers and $b$ does not equal $1$ , then $\log_{b} (x) = y$ is equivalent to $b^{y} = x$ .

$3^{x} = 9$

Create equivalent expressions in the equation that all have equal bases.

$3^{x} = 3^{2}$

Since the bases are the same, the two expressions are only equal if the exponents are also equal.

$x = 2$

The variable $x$ is equal to $2$ .

$f (9) = 2$

The final answer is $2$ .

$2$

Convert $2$ to decimal.

$y = 2$

The log function can be graphed using the vertical asymptote at $x = 0$ and the points $(1, 0), (3, 1), (9, 2)$ .

Vertical Asymptote: $x = 0$

$\begin{array}{c} x & y \\ 1 & 0 \\ 3 & 1 \\ 9 & 2 \end{array}$

Vertical Asymptote: $x = 0$

$\begin{array}{c} x & y \\ 1 & 0 \\ 3 & 1 \\ 9 & 2 \end{array}$

Step 3

Plot each graph on the same coordinate system.

$f (x) = 3^{x}$

$f^{- 1} (x) = \log_{3} (x)$

Step 4

Graph f(x)=3^x , f^-1(x) = log base 3 of x

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