The function is given by \( f(x) = 6 + 3x - 5x^2 \). To find the critical numbers, we first compute the derivative of the function:
\[
f'(x) = 3 - 10x
\]
Step 2: Set the Derivative to Zero
Next, we set the derivative equal to zero to find the critical points:
\[
3 - 10x = 0
\]
Solving for \( x \), we get:
\[
10x = 3 \quad \Rightarrow \quad x = \frac{3}{10}
\]
Step 3: Identify Critical Numbers
The critical number of the function \( f(x) \) is \( x = \frac{3}{10} \).