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

Multiple Choice

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

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