# Substituting f(x)

• June 3rd 2009, 05:33 AM
Envy
Substituting f(x)
I know this is really basic why does

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

equal

$
-2$

and not

$-8$
• June 3rd 2009, 05:35 AM
Prove It
Quote:

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

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

$= -2$.
• June 3rd 2009, 05:38 AM
Joel
Substituting 2 into the equation

http://www.mathhelpforum.com/math-he...d5227ede-1.gif

-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