Two people, A and B, use iron nets of the same length to surround the vegetable garden. A is surrounded by a square, and B is surrounded by a rectangle. One side of the rectangle is 3 feet longer than the side of the square. What is the difference in the area of the two vegetable gardens in square feet?
A，B两人用同样长的铁网围菜园，A围成正方形，B围成长方形，长方形一边比正方形边长多3尺，那么两菜园面积相差多少平方尺．
<result>9</result>