Prove the following statement:

Anyone know how to do this question?

Hi, attached is my solution, although I believe there might be an easier way:

Question \tan A \tan \left(A-60^{\circ}\right)+\tan A \tan \left(A+60^{\circ}\right)+\tan \left(A-60^{\circ}\right) \tan \left(A+60^{\circ}\right)=-3

\tan A \tan \left(A-60^{\circ}\right)+\tan A \tan \left(A+60^{\circ}\right)+\tan \left(A-60^{\circ}\right) \tan \left(A+60^{\circ}\right)=-3

Okay, I understand now, tqvm!