-3 - 5/2 = ?
5.5
5.05
-5.5
-1/2
If |z1|=|z2|=|z3|=|z4|=1 and z1+z2+z3+z4=0 then least value of the expression E=|z1−z2|2+|z2−z3|2+|z3−z4|2+|z4−z1|2 is