Simplify first and then evaluate: y(x+y)+(xy)**2-x**2-2y**2, where x=-(1/3), y=3.
先化简再求值：y(x+y)+(x-y)**2-x**2-2y**2，其中x=-(1/3)，y=3．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">-(1/3)</gadget>
<output>-1/3 = around -0.333333</output>

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

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

<result>1</result>