Questions: Determine whether the function is one-to-one. If it is, find a formula for its inverse.
f(x)=x^3-5
Is the function one-to-one?
Yes
No
Select the correct choice below and fill in any answer boxes within your choice.
A. The inverse function is f^(-1)(x)=
B. There is no inverse function.
Transcript text: Determine whether the function is one-to-one. If it is, find a formula for its inverse.
\[
f(x)=x^{3}-5
\]
Is the function one-to-one?
Yes
No
Select the correct choice below and fill in any answer boxes within your choice.
A. The inverse function is $f^{-1}(x)=$ $\square$
B. There is no inverse function.
Solution
Solution Steps
To determine if the function \( f(x) = x^3 - 5 \) is one-to-one, we need to check if it is strictly increasing or decreasing. A function is one-to-one if it passes the horizontal line test, which can be verified by checking the derivative. If the derivative is always positive or always negative, the function is one-to-one. If the function is one-to-one, we can find its inverse by solving the equation \( y = x^3 - 5 \) for \( x \).
Step 1: Determine if the Function is One-to-One
A function is one-to-one if each output is produced by exactly one input. For a function \( f(x) = x^3 - 5 \), we can determine if it is one-to-one by checking if it is strictly increasing or decreasing.
The derivative of \( f(x) \) is:
\[
f'(x) = \frac{d}{dx}(x^3 - 5) = 3x^2
\]
Since \( 3x^2 \geq 0 \) for all \( x \) and \( f'(x) = 0 \) only at \( x = 0 \), the function is non-decreasing and strictly increasing for \( x \neq 0 \). Therefore, \( f(x) = x^3 - 5 \) is a one-to-one function.
Step 2: Find the Inverse Function
To find the inverse function, we need to solve the equation \( y = x^3 - 5 \) for \( x \).
Start with the equation:
\[
y = x^3 - 5
\]
Add 5 to both sides:
\[
y + 5 = x^3
\]
Take the cube root of both sides:
\[
x = \sqrt[3]{y + 5}
\]
Thus, the inverse function is:
\[
f^{-1}(x) = \sqrt[3]{x + 5}
\]
Final Answer
The function is one-to-one, and the inverse function is:
\[
\boxed{f^{-1}(x) = \sqrt[3]{x + 5}}
\]