If each side of a square lawn is increased by 5 meters, it will still be a square lawn after the expansion, and the area is 425 square meters larger than the original square lawn. Find the side length of the original square lawn.
一块正方形的草地如果每边增加5米，扩大后仍为一块正方形草地，面积比原来正方形草地多425平方米，求原来的正方形草地的边长．
<gadget id="calculator">5 * 5</gadget>
<output>25</output>

<gadget id="calculator">425 - 25</gadget>
<output>400</output>

<gadget id="calculator">400 / 2 / 5</gadget>
<output>40</output>

<result>40</result>