Extend the edge of △ABC to A 1 so that b is the midpoint of the line segment A 1. In the same way, extending the edge BC to get the point B 1 and extending the edge to get the point C 1 is called the first extension. Then extend △A 1 B 1 C 1 outward according to the above method to get △A2 B2 C2, and so on to get △ anbcnn, and study the area relationship between △ anbcnn and △ABC. (not less than 200 words)

Answer: followed by a B 1

∫AC = AC 1

∴s△b 1ac=s△b 1ac 1

∫CB 1 = CB

∴S△B 1AC=S△ABC

∴S△B 1C 1C=2S△ABC

In the same way, we can get s △ aa1c1= s △ ba1b1= 2s △ ABC.

∴s△a 1b 1c 1=7s△abc

Similarly, s △ A2B2C2 = 7s △ a1b1c1= 49s △ ABC.

∴S△AnBnCn=7^nS△ABC

The express train and the local train travel from the express train to the local train, and the express train travels 2/3 of the whole journey. The local train is 0/80km away from the destination/kloc-. The two trains continued to travel at the original speed, and the local train traveled 6/7 of the whole journey. How many meters is the whole journey?

Answer: the express train has finished the whole journey, and the local train has gone 6/7 of the whole journey;

Compared with the same period:

When the express train is 2/3 of the whole journey, the local train should have gone 6/7*2/3 (that is, 4/7), leaving 3/7, which is the known condition of 180, and the whole journey is 180/(3/7) = 420!