Define a new operation "▽" for two integers a and b: a▽b=((2a-b)/((a+b)*(ab))), find 6▽4+9▽8.
对两个整数a和b定义新运算"▽"：a▽b=((2a-b)/((a+b)*(a-b)))，求6▽4+9▽8．
<gadget id="calculator">2 * 6</gadget>
<output>12</output>

<gadget id="calculator">12 - 4</gadget>
<output>8</output>

<gadget id="calculator">6 + 4</gadget>
<output>10</output>

<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">8 / 20</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">2 * 9</gadget>
<output>18</output>

<gadget id="calculator">18 - 8</gadget>
<output>10</output>

<gadget id="calculator">9 + 8</gadget>
<output>17</output>

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

<gadget id="calculator">17 * 1</gadget>
<output>17</output>

<gadget id="calculator">10 / 17</gadget>
<output>10/17 = around 0.588235</output>

<gadget id="calculator">(2/5) + (10/17)</gadget>
<output>84/85 = around 0.988235</output>

<result>84/85 = around 0.988235</result>