If f(x)=ax^2-x, and f(4)=28, what is f(-2)?

Question

(A): 1
(B): 2
(C): 4
(D): 8
(E): 10

ArunSharma12 · Answer

f(4)= 28 =  a*(4)^2-4=a*16-4 
a = 2

f(-2) =  2*(-2)^2+2  = 10
Ans: E

globaldesi · Answer

f(x)=ax^2-x  = put x = 4
16a- 4= 26
or a 2
thus 
f(-2) = 8+2 = 10
(E)

EgmatQuantExpert · Answer

Solution

Given  
In this question, we are given that
 • A function f(x), defined as  f(x) = ax^2 – x 
• Also, f(4) = 28

To find  
We need to determine
 • The value of f(-2)

Approach and Working out  
As f(4) = 28, we can write
 •  f(4) = a * 4^2 – 4 = 16a – 4 = 28 
Or, 16a = 32
Or, a = 2

Hence,  f(x) = 2x^2 – x 
Therefore,  f(-2) = 2 * (-2)^2 – (-2) = 8 + 2 = 10

Thus, option E is the correct answer.

Correct Answer: Option E

hiranmay · Answer

If f(x)=ax^2-x, and f(4)=28, what is f(-2)?

(A): 1
(B): 2
(C): 4
(D): 8
(E): 10 -->   correct : f(4)= a*4^2-4 = 16a-4 =28 => a = 2, so f(-2)= a*(-2)^2-(-2)=4a+2=4*2+2=10

bumpbot · Answer

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If f(x)=ax^2-x, and f(4)=28, what is f(-2)?

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If f(x)=ax^2-x, and f(4)=28, what is f(-2)?

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