kailiekleeves kailiekleeves
  • 11-11-2020
  • Mathematics
contestada

Which pair of complex numbers has a real-number product?

O (1 + 2i) (8i)

0 (1 + 2i) (2 - 5i)

O (1 + 2i) (1 – 2i)

O (1 + 2i)(4i)

Respuesta :

jimrgrant1 jimrgrant1
  • 11-11-2020

Answer:

(1 + 2i)(1 - 2i)

Step-by-step explanation:

Multiplying a complex number and its conjugate results in a real number.

Thus

1 + 2i and 1 - 2i are conjugates

(1 + 2i)(1 - 2i) ← expand using FOIL

= 1 - 2I + 2I - 4I² [ note i² = - 1 ]

= 1 - 4(- 1)

= 1 + 4

= 5 ← a real number

Answer Link
Numinum
Numinum Numinum
  • 18-05-2022

Answer:

C

Step-by-step explanation:

C

Answer Link

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