Answer :

To evaluate the function [tex]\( f(x) = 5x^2 \)[/tex] at [tex]\( x = 3 \)[/tex], follow these steps:

1. Substitute [tex]\( x = 3 \)[/tex] into the function:
[tex]\[ f(3) = 5 (3)^2 \][/tex]

2. Calculate the square of 3:
[tex]\[ 3^2 = 9 \][/tex]

3. Multiply the result by 5:
[tex]\[ 5 \times 9 = 45 \][/tex]

So, the value of the function [tex]\( f(x) \)[/tex] when [tex]\( x = 3 \)[/tex] is 45.

Therefore, the correct answer is:
[tex]\[ \boxed{45} \][/tex]