i + i2 + i3 +_____ 1000 terms
i.e i + i2 + i3 + i4 _____ + i1000
= i + i2 – i + 1 + i5 _____ + i1000
= i – 1 – i + 1 + i5 + _______ + i1000
= 0 + i5 + i6 + ________ + i100
Similarly, sum of next form terms is also zero. (∵ 1000 = 4(250)
i.e multiple of 4
Hence, i + i2 + i3 +_____ i1000 = 0