Tolong selesaikan dengan melengkapi kuadrat sempurna

Tolong selesaikan dengan melengkapi kuadrat sempurna

$begin{array}{rcl}2x^2-3x-9&=&0\~\x^2-frac{3}{2}x-frac{9}{2}&=&0\~\x^2-frac{3}{2}x&=&frac{9}{2}\~\x^2-frac{3}{2}x+left(frac{1}{2}times frac{3}{2}right)^2&=&frac{9}{2}+left(frac{1}{2}times frac{3}{2}right)^2\~\x^2-frac{3}{2}x+frac{9}{16}&=&frac{9}{2}+frac{9}{16}\~\left(x-frac{3}{4}right)^2&=&frac{81}{16}\~\x-frac{3}{4}&=&mp sqrt{frac{81}{16}}\~\x&=&frac{3}{4}mp frac{9}{4}\~\x=frac{3}{4}-frac{9}{4}&atau&x=frac{3}{4}+frac{9}{4}\~\x=-frac{6}{4}&atau&x=frac{12}{4}\~\x=-frac{3}{2}&atau&x=3end{array}$