Questions: Find the critical numbers of the function.
f(x)=x^3+3 x^2-45 x
x=
Transcript text: Find the critical numbers of the function.
\[
\begin{array}{r}
f(x)=x^{3}+3 x^{2}-45 x \\
x=\square
\end{array}
\]
Solution
Solution Steps
To find the critical numbers of the function \( f(x) = x^3 + 3x^2 - 45x \), we need to follow these steps:
Compute the first derivative of the function, \( f'(x) \).
Set the first derivative equal to zero and solve for \( x \).
The solutions to this equation are the critical numbers.
Step 1: Find the First Derivative
We start with the function \( f(x) = x^3 + 3x^2 - 45x \). The first derivative is calculated as follows:
\[
f'(x) = 3x^2 + 6x - 45
\]
Step 2: Set the First Derivative to Zero
To find the critical numbers, we set the first derivative equal to zero:
\[
3x^2 + 6x - 45 = 0
\]
Step 3: Solve for Critical Numbers
We can simplify the equation by dividing all terms by 3:
\[
x^2 + 2x - 15 = 0
\]
Next, we factor the quadratic:
\[
(x - 3)(x + 5) = 0
\]
Setting each factor to zero gives us the critical numbers:
\[
x - 3 = 0 \quad \Rightarrow \quad x = 3
\]
\[
x + 5 = 0 \quad \Rightarrow \quad x = -5
\]
Final Answer
The critical numbers of the function are \\(\boxed{-5, 3}\\).