Question

For which equation will f(-2)= -6?

Answer 1

Answer:

C. $f(x)=4x^3+6x^2-x$

Step-by-step explanation:

Lets plug in -2 into each of these equation to see which one gives us the solution of -6

A. $f(x)=x^3+x$

$f(-2)=(-2)^3+(-2)\\\\f(-2)=-8-2\\\\f(-2)=-10$

B. $f(x)=x^4-5x$

$f(-2)=(-2)^4-5(-2)\\\\f(-2)=16+10\\\\f(-2)=26$

C. $f(x)=4x^3+6x^2-x$

$f(-2)=4(-2)^3+6(-2)^2-(-2) \\\\f(-2)=4(-8)+6(4)+2\\\\f(-2)=-32+24+2\\\\f(-2)=-6$

D. $f(x)=-3x^3-4x^2+4x$

$f(-2)=-3(-2)^3-4(-2)^2+4(-2)\\\\f(-2)=-3(-8)-4(4)-8\\\\f(-2)=24-16-8\\\\f(-2)=0$

As we can see, function C was the only one that gave us the value of -6, so that is our answer.

Answer 2

Answer:the correct option is C

Step-by-step explanation:

To find the equation for which

f(-2) = - 6, we will substitute x = - 2 into each of the equations. It becomes

A) f(x) = -2^3 + (-2) = - 8 - 2 = -10

B) f(x) = (-2)^4 -5(-2) = 16 + 10 = 26

C) f(x) = 4x^3 + 6x^2 - x = 4(-2)^3 + 6(-2)^2 - (-2) = (4 × -8) + (6 × 4) + 2

= - 32 + 24 + 2 = - 6

D) f(x) = - 3(-2)^3 - 4(-2)^2 + 4(-2) = (-3 × - 8) - (4 × 4) + (4 × -2) = 24 - 16 - 8 = 0

Therefore, the correct option is C