When a=5, b=0.5, what is the value of 0.4a**2-2b
当a=5，b=0.5时，0.4a**2-2b的值是多少
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">0.4 * 25</gadget>
<output>10</output>

<gadget id="calculator">2 * 0.5</gadget>
<output>1</output>

<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<result>9</result>