Questions: Determine the location of each local extremum of the function.
f(x)=-x^3-9x^2-24x+1
What is/are the local minimum/minima? Select the correct choice below and, if necessary, fill in the answer box to complete your choice.
Transcript text: Determine the location of each local extremum of the function.
\[
f(x)=-x^{3}-9 x^{2}-24 x+1
\]
What is/are the local minimum/minima? Select the correct choice below and, if necessary, fill in the answer box to complete your choice.
Solution
Solution Steps
To find the local extrema of the function \( f(x) = -x^3 - 9x^2 - 24x + 1 \), we need to follow these steps:
Compute the first derivative of the function, \( f'(x) \).
Find the critical points by setting \( f'(x) = 0 \) and solving for \( x \).
Use the second derivative test to determine the nature of each critical point (local minimum or maximum).
Step 1: Find the First Derivative
The first derivative of the function \( f(x) = -x^3 - 9x^2 - 24x + 1 \) is calculated as follows:
\[
f'(x) = -3x^2 - 18x - 24
\]
Step 2: Determine Critical Points
To find the critical points, we set the first derivative equal to zero:
\[
-3x^2 - 18x - 24 = 0
\]
Factoring or using the quadratic formula, we find the critical points:
\[
x = -4, \quad x = -2
\]
Step 3: Find the Second Derivative
Next, we compute the second derivative to determine the nature of the critical points:
\[
f''(x) = -6x - 18
\]
Step 4: Classify the Critical Points
We evaluate the second derivative at each critical point:
The local minimum occurs at \( x = -4 \) and the local maximum occurs at \( x = -2 \). Thus, the final answer is:
\[
\boxed{x = -4} \quad \text{(local minimum)}
\]