# If f(x)=3(x+5)+4/x, what is f(a+2)?

##### 1 Answer
Jan 2, 2017

To determine $f \left(a + 2\right)$ you need to substitute $\textcolor{red}{a + 2}$ for each occurrence of $x$ in the given function. See below for full explanation.

#### Explanation:

If

$f \left(\textcolor{red}{x}\right) = 3 \left(\textcolor{red}{x} + 5\right) + \frac{4}{\textcolor{red}{x}}$

Then

$f \left(\textcolor{red}{a + 2}\right) = 3 \left(\textcolor{red}{a + 2} + 5\right) + \frac{4}{\textcolor{red}{a + 2}}$

Simplifying gives:

$f \left(\textcolor{red}{a + 2}\right) = 3 \left(a + 7\right) + \frac{4}{a + 2}$