When x=(1/4), y=(1/5), find the value of (x+y)(xy).
当x=(1/4)，y=(1/5)时，求(x+y)(x-y)的值．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/4) + (1/5)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">(1/4) - (1/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(9/20) * (1/20)</gadget>
<output>9/400 = around 0.0225</output>

<result>9/400 = around 0.0225</result>