Greatest negative integral value of n for which (1+i1−i)n = 1 is
-4
1+i1−i can be brought to standard form by multiplying both numerator & denominator by 1+i
(1+i)(1−i)(1+i)(1+i) = (1+i)21+1 = 2i2 = i
⇒ in = 1 for n = 4k
i.e., n = ......... , -12,-8,-4,0,4,8,12,.........
So,greatest negative integer among above numbers is -4