课余小明解一道初中数学竞赛题:如图1,△ABC内有一点O,过O作各边的平行线,把△ABC分成三个三角形和三个平行四边形.若三个三角形的面积分别是1,1,2,求△ABC的面积.(2004,四川)他的解答过程如下:如图2,易知三个三角形与△ABC均相似.记△ABC的面积为S,则√S1√S+√S2√S+√√S S3 After class Xiaoming solved a junior high school math contest title: As shown in Figure 1, △ABC has a little O, over O for each side of the parallel line, the △ABC is divided into three triangles and three parallelograms. If the area of ​​the three triangles are 1,1,2, find the area of ​​△ABC. (2004, Sichuan) His solution process is as follows: As shown in Figure 2, it is easy to know that the three triangles are similar to △ABC. The area of ​​△ABC is S, then √S1√. S+√S2√S+√√S S3