Simplify first, then evaluate: 3(x**2-2xy)-(3x**2-2y+2(xy+y)), where x=-(1/2), y=-3.
先化简，再求值：3(x**2-2xy)-(3x**2-2y+2(xy+y))，其中x=-(1/2)，y=-3．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">-(1/2)</gadget>
<output>-1/2 = around -0.5</output>

<gadget id="calculator">8 * (-1/2) * (-3)</gadget>
<output>12</output>

<result>12</result>