Answer
$x+4-\frac{15}{x+4}$
Work Step by Step
We have to perform the division
$$\dfrac{f(x)}{x-a}=\dfrac{x^2+8x+1}{x+4}.$$
We use synthetic division.
First we write the coefficients of $f$ in order of descending coefficients and write the value at which $f$ is being evaluated to the left.
Then we bring down the leading coefficient, multiply the leading coefficient by the $x$-value, write the product under the second coefficient, and add.
Then we multiply the previous sum by the $x$-value, write the product under the third coefficient, and add. Perform this for all the remaining coefficients. We get the value of $f$ at the given $x$-value as the final sum.
$$\dfrac{x^2+8x+1}{x+4}=x+4-\dfrac{15}{x+4}.$$
