Q28 / 108 · NTA Abhyas (JEE Main) 2020 · Mathematics · Complex Number

The value of ∑k=199ik!+ωk! is (where, i=-1 and ω is non-real cube root of unity)

  • A
    190+ω
  • B
    192+ω2
  • Correct answer
    C
    190+i
  • D
    192+i

Solution

∑k=199ik!+∑k=199ωk!
∑k=199ik!=i1!+i2!+i3!+i4!+…+i99!
=i-1+i6+1+1+1+…+1
=i-2+96=i+94
∑k=199ωk!=ω1+ω2!+ω3!+ω4!+…+ω99!
=ω+ω2+1+1+1+…+1=96
Sum =i+94+96=i+190

Hence, the correct answer is option: 'C'.

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