If α , β ∈ R are such that 1 - 2 i (here i 2 = - 1 ) is a root of z 2 + α z + β = 0 , then α - β is equal to:

Step-by-step solution

∵ α , β ∈ R ⇒ other root is 1 + 2 i α = - ( sum of roots ) = - 1 - 2 i + 1 + 2 i = - 2 β = product of roots = 1 - 2 i 1 + 2 i = 5 ∴ α - β = - 7 option 1