alleryIf z and z̄ are roots of a quadratic with real coefficients, then sum z + z̄ equals:
A2 Re(z) (twice real part)
B0
C|z|
DImaginary
Answer & Solution
Correct answer: A. 2 Re(z) (twice real part)
We have z + z̄ = (a + ib) + (a - ib).
That is z + z̄ = 2a.
So z + z̄ = 2 Re(z).
Complex conjugate pairs are roots of real-coefficient polynomials.
Sum and product of conjugates are both real.
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