# Math Help - Substituting f(x)

1. ## Substituting f(x)

I know this is really basic why does

$
f(2)=-4{x}^{-1}$

equal

$
-2$

and not

$-8$

2. Originally Posted by Envy
I know this is really basic why does

$
f(2)=-4{x}^{-1}$

equal

$
-2$

and not

$-8$
Your question does not make any sense.

If $f(x) = -4x^{-1}$ what does $f(2)$ equal?

Let $x = 2$.

You would have $f(2) = -4(2)^{-1}$

$= -4\left(\frac{1}{2}\right)$

$= -2$.

3. Substituting 2 into the equation

-4 * ( 2 to the power of -1 )

2 to the power of -1 is the same as 1 / 2

so -4 * 1/2 = -2 and not -8