After increasing the length of a rectangle by 6 decimeters and its width by 9 decimeters, a square with an area 201 square decimeters larger than the original rectangle is obtained. What is the side length of the square?
把一个长方形的长增加6分米，宽增加9分米后，得到一个面积比原长方形多201平方分米的正方形，正方形的边长是多少．
<gadget id="calculator">2 + 15</gadget>
<output>17</output>

<result>17</result>