Find the Largest Open Interval Where the Function Is Changing $f(x)=\frac{1}{4} x^{2}-\frac{1}{2} x$

Multiple Choice

Find the largest open interval where the function is changing as requested.
-Increasing $f(x) =\frac{1}{4} x^{2}-\frac{1}{2} x$

A) $(-\infty,-1)$
B) $(-\infty, \infty)$
C) $(1, \infty)$
D) $(-1,1)$