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Complex Numbers and Quadratic Equations — MATHS STD 11 Science — Question

Rajasthan BoardEnglish MediumSTD 11 ScienceMATHSComplex Numbers and Quadratic Equations1 Mark
MCQ
The sum of two complex numbers a + ib and c + id is purely imaginary if
  • A
    a + c = 0
  • B
    a + d = 0
  • C
    b + d = 0
  • D
    b + c = 0
✓

Answer

  1. a + c = 0

Solutions:

It is given that

z1​ = a + ib and

z2​ = c + id

z1​ + z2​ = (a+c) + i(b+d)

z1 ​+ z2​ is purely imaginary. (Given)

Then the real part has to be 0.

Hence

a + c = 0.

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