/sci/ - Science & Math

Could you guys give me your subjective rating of the difficulty of this problem?
I don't need a solution, I'd just like you to tell me how difficult this problem seems to you and maybe at what level of education one should be to solve this problem
The problem follows as such:

In the triangle ABC, angle BAC is two times bigger than angle ABC. Show that the following equation is true:
BC^2 - AC^2 = AB * AC