# Inverse Function

• Aug 10th 2010, 08:22 PM
soni
Inverse Function
f(x)=4x+6; g(x)=x/4-6 is the function inverse of eachother.
• Aug 10th 2010, 08:49 PM
eumyang
\begin{aligned}
f(x) &= 4x+6 \\
g(x) &= \dfrac{x}{4} - 6
\end{aligned}

I guess you want to know if f(x) and g(x) are inverses of each other? If
f(g(x)) = x and g(f(x)) = x then the answer is yes.

I'll setup both for you.
$f(g(x))= 4\left( \dfrac{x}{4} - 6 \right) + 6$
...
Will f(g(x)) = x?

And
$g(f(x))= \dfrac{4x + 6}{4} - 6$
...
Will g(f(x)) = x?
• Aug 10th 2010, 08:51 PM
masoug
The very best way is to take one of the functions and "plug" it into the other
So in this case, $f(x)=4x+6$ and $g(x)=\frac{x}{4}-6$, $f(g(x))$ must equal $x$.

So the inverse of $f(x)=4x+6$ should be:
$g(x)=\frac{x-6}{4}$

Checking that would be:
$f(x)=4(\frac{x-6}{4})+6$
Cancel out the four,
$f(x)=x-6+6$
And simplify,
$f(x)=x$
and so it checks, $g(x)=\frac{x-6}{4}$ is the inverse function.

-Masoug
• Aug 10th 2010, 09:15 PM
soni
Quote:

Originally Posted by eumyang
Uhm, this is not a geometry question.

\begin{aligned}
f(x) &= 4x+6 \\
g(x) &= \dfrac{x}{4} - 6
\end{aligned}

I guess you want to know if f(x) and g(x) are inverses of each other? If
f(g(x)) = x and g(f(x)) = x then the answer is yes.

I'll setup both for you.
$f(g(x))= 4\left( \dfrac{x}{4} - 6 \right) + 6$
...
Will f(g(x)) = x?

And
$g(f(x))= \dfrac{4x + 6}{4} - 6$
...
Will g(f(x)) = x?

Thanx