High School

Given the function [tex]f(x) = -5x^2 - x + 20[/tex], find [tex]f(3)[/tex].

A. [tex]-28[/tex]
B. [tex]-13[/tex]
C. 62
D. 64

Answer :

To find [tex]\( f(3) \)[/tex] for the function [tex]\( f(x) = -5x^2 - x + 20 \)[/tex], we will substitute [tex]\( x = 3 \)[/tex] into the function and evaluate it step-by-step.

1. Start with the function:
[tex]\( f(x) = -5x^2 - x + 20 \)[/tex].

2. Substitute [tex]\( x = 3 \)[/tex] into the function:
[tex]\( f(3) = -5(3)^2 - (3) + 20 \)[/tex].

3. Calculate [tex]\( 3^2 \)[/tex]:
[tex]\( 3^2 = 9 \)[/tex].

4. Multiply by [tex]\(-5\)[/tex]:
[tex]\(-5 \times 9 = -45\)[/tex].

5. Substitute back into the expression:
[tex]\( f(3) = -45 - 3 + 20 \)[/tex].

6. Simplify step by step:
- First, calculate [tex]\(-45 - 3\)[/tex]:
[tex]\(-45 - 3 = -48\)[/tex].

7. Then add 20:
[tex]\(-48 + 20 = -28\)[/tex].

Therefore, the value of [tex]\( f(3) \)[/tex] is [tex]\(-28\)[/tex].