Giải thích các bước giải:
a) y=2x²-$\frac{1}{2}$x+$\frac{1}{4}$
f(3)=2.3²-$\frac{1}{2}$.3+ $\frac{1}{4}$
=$\frac{67}{4}$
b) f(x)=$\frac{1}{4}$ <=> 2x²-$\frac{1}{2}$x+ $\frac{1}{4}$= $\frac{1}{4}$
<=> 2x²-$\frac{1}{2}$x=0
<=> \(\left[ \begin{array}{l}x=0\\x=\frac{1}{4}\end{array} \right.\)
c) f(x)<$\frac{1}{4}$ <=> 2x²-$\frac{1}{2}$x+ $\frac{1}{4}$< $\frac{1}{4}$
<=> 2x²-$\frac{1}{2}$x<0
<=> 0<x<$\frac{1}{4}$