Subject:  Precalculus

Multiply (3 + 2i)·(1 − i)

Use the FOIL method and i² = −1 to multiply two complex numbers.

Answer 5 − i

Solution

  1. Inputs z₁ = 3 + 2i, z₂ = 1 − i
  2. Multiply (FOIL) (ac − bd) + (ad + bc)i
  3. Real part 3·1 − 2·-1 = 5
  4. Imag part 3·-1 + 2·1 = -1
  5. Result 5 − i
  6. Modulus |z| = √(re² + im²) = 5.09902

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