$解：(1)原式=2×3^{2}-4×3×(-\frac{1}{2})^{2}+4×(-\frac{1}{2})$
$=18-12×\frac{1}{4}+(-2)$
$=18-3+(-2)$
$=13$
$(2)原式=\frac{3^{2}+4×3×(\displaystyle{-\frac{1}{2})}}{2×3×(-\displaystyle{\frac{1}{2})}-(-\displaystyle{\frac{1}{2}})^{2}}$
$=\frac{9-6}{-3-\displaystyle{\frac{1}{4}}}$
$=-\frac{3}{\displaystyle{\frac{13}{4}}}$
$=-\frac{12}{13}$
