Find the value of following expression:

i49 + i68 + i89 + i110

i49 + i68 + i89 + i110 = i(48 + 1) + i68 + i(88 + 1) + i(108 + 2)


= (i4)12 × i + (i4)17 + (i4)11 × i + (i4)27 × i2


= i + 1 + i – 1 = 2i


[since i4 = 1, i2 = – 1]


i49 + i68 + i89 + i110 = 2i


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