Calculation: (a+2b)(a-2b)-(1/2)b(a-8b)
计算：(a+2b)(a-2b)-(1/2)b(a-8b)
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 - (1/2)</gadget>
<output>3/2 = around 1.5</output>

<result>3/2 = around 1.5</result>