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
