#### Answer

$f(x)=\frac{1}{2}x-1$

#### Work Step by Step

A linear function has the form $f(x)=ax+b$, with $a=$slope and $b=$y-intercept.
Since the slope is $\frac{1}{2}$, $a=\frac{1}{2}$.
Since the y-intercept is -1, $b=-1$.
Thus the function is:
$f(x)=\frac{1}{2}x-1$