If a square wire frame with a side length of a cm is changed into a rectangular frame with the same wire length, the area is reduced by 169 cm2. Then, how many centimeters is the length of the rectangle longer than the side length of the square?
把一个边长为a厘米的正方形铁丝框架，改成铁丝长度不变的长方形框架，面积比原来减少169平方厘米，那么，长方形的长比正方形的边长长多少厘米．
<result>13</result>