10. If [tex]\( f(x) = 2x^2 - x \)[/tex], what is [tex]\( f(-6) \)[/tex]?

A. [tex]\(-30\)[/tex]
B. [tex]\(-78\)[/tex]
C. [tex]\(18\)[/tex]
D. [tex]\(78\)[/tex]



Answer :

To find [tex]\( f(-6) \)[/tex] given the function [tex]\( f(x) = 2x^2 - x \)[/tex], we need to substitute [tex]\( x \)[/tex] with [tex]\(-6\)[/tex] and evaluate the expression step-by-step:

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

2. Substitute [tex]\( x = -6 \)[/tex] into the function:
[tex]\[ f(-6) = 2(-6)^2 - (-6) \][/tex]

3. Calculate [tex]\((-6)^2\)[/tex]:
[tex]\[ (-6)^2 = 36 \][/tex]

4. Multiply this result by 2 (since [tex]\( 2 \cdot 36 \)[/tex]):
[tex]\[ 2 \cdot 36 = 72 \][/tex]

5. The function now looks like:
[tex]\[ f(-6) = 72 + 6 \][/tex]

6. Add 6 to 72:
[tex]\[ 72 + 6 = 78 \][/tex]

Therefore, the value of [tex]\( f(-6) \)[/tex] is [tex]\( 78 \)[/tex].

Among the answer choices, the correct one is:
[tex]\[ \boxed{78} \][/tex]