Let α, β be real and z be a complex number. If z2+2z + β = 0 has two distinct roots, on the line Re(z) = 1 then it is necessary that
A
βϵ[0,1)
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B
βϵ[−1,0)
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C
|β| = 1
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D
βϵ[1, ∞)
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Solution
The correct option is Dβϵ[1, ∞) Let roots be p + iq and p - iq, p,q ϵ R Some roots lie on the line Re(z) = 1 ⇒ p = 1 product of roots = p2 + q2 = p = 1 + q2 ⇒βϵ[1,∞) (q ≠ 0 ∵ roots are unequal)