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MathsMediumMCQ2015 · 10 Apr Online

Q62.If 2 + 3i is one of the roots of the equation 2x3 −9x2 + kx −13 = 0, k ∈R, then the real root of this equation (where i2 = −1) : (1) Exists and is equal to 1 (2) Does not exist 2 (3) Exists and is equal to 1 (4) Exists and is equal to −12

What This Question Tests

This question tests the property that complex roots of a polynomial with real coefficients always occur in conjugate pairs, and the relations between roots and coefficients for a cubic equation to find the real root.

Concepts Tested

Conjugate root theoremSum and product of roots of polynomial

Formulas Used

If P(x) has real coefficients and (a+bi) is a root, then (a-bi) is also a root.

For ax³+bx²+cx+d=0 with roots α,β,γ: α+β+γ = -b/a, αβγ = -d/a

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