If the flag rope is straightened, the lower end is on the ground, 5 meters away from the bottom of the flagpole, and the length of the flagpole is 5 meters, then the flag rope, the flagpole and the ground form a right triangle, and the Pythagorean theorem can be used.
Namely: x? +5? =(x+ 1)？
The solution is x= 12.
A: flagpole length12m.