1. The problem statement, all variables and given/known data z1, z2 are complex numbers. If z1z2 =/= -1 and |z1| = |z2| = 1 then number : z1 + z2 ________ 1 + z1z2 is real. 2. Relevant equations 3. The attempt at a solution z1 = (a+bi), z2 = (c+di) Should i use this extended form or is there a shorter path ? because it's pretty long.