Define the operation "*" as: a*b=a+b/(ab), then (6*4)*4=how much.
定义运算"*"为：a*b=a+b/(a-b)，则(6*4)*4=多少．
<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">6 + 2</gadget>
<output>8</output>

<gadget id="calculator">8 - 4</gadget>
<output>4</output>

<gadget id="calculator">4 / 4</gadget>
<output>1</output>

<gadget id="calculator">8 + 1</gadget>
<output>9</output>

<result>9</result>