Evaluate f(x+4)=x/(x^2+1)

$f (x + 4) = \frac{x}{x^{2} + 1}$

Divide each term in $f (x + 4) = \frac{x}{x^{2} + 1}$ by $x + 4$ .

$\frac{f (x + 4)}{x + 4} = \frac{\frac{x}{x^{2} + 1}}{x + 4}$

Simplify the left side.

Cancel the common factor of $x + 4$ .

Cancel the common factor.

$\frac{f (x + 4)}{x + 4} = \frac{\frac{x}{x^{2} + 1}}{x + 4}$

Divide $f$ by $1$ .

$f = \frac{\frac{x}{x^{2} + 1}}{x + 4}$

Simplify the right side.

Multiply the numerator by the reciprocal of the denominator.

$f = \frac{x}{x^{2} + 1} \cdot \frac{1}{x + 4}$

Multiply $\frac{x}{x^{2} + 1}$ by $\frac{1}{x + 4}$ .

$f = \frac{x}{(x^{2} + 1) (x + 4)}$