Elementary Algebra

-$\frac{1}{4}$
$x^{2}$ - 3xy - 2$y^{2}$ = We substitute x=$\frac{1}{2}$ and y=$\frac{1}{4}$ into the expression and simplify: $(\frac{1}{2})^{2}$ - 3 $\times$ $\frac{1}{2}$ $\times$ $\frac{1}{4}$ - 2 $\times$ $(\frac{1}{4})^{2}$ = $\frac{1}{4}$ - $\frac{3}{8}$ - $\frac{2}{16}$ = We need to change the denominator of each fraction to 16. $\frac{1}{4}$ $\times$ $\frac{4}{4}$ - $\frac{3}{8}$ $\times$ $\frac{2}{2}$- $\frac{2}{16}$ = $\frac{4}{16}$ - $\frac{6}{16}$ - $\frac{2}{16}$ = - $\frac{4}{16}$ = -$\frac{1}{4}$