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Complex Numbers and Quadratic Equations — Maths STD 11 Science — Question

CBSE BoardEnglish MediumSTD 11 ScienceMathsComplex Numbers and Quadratic Equations1 Mark
MCQ
Roots of a quadratic equation are imaginary when discriminant is $..............?$
  • A
    zero
  • B
    greater than zero
  • ✓
    less than zero
  • D
    greater than or equal to zero
✓

Answer

Correct option: C.
less than zero
For a quadratic equation, $ax^2 + bx + c = 0$, discriminant is $b^2$-4ac.
Roots are $\frac{-\text{b}\pm\sqrt{b^2 -4\text{ac}}}{2\text{a}}$ for imaginary roots, radical is negative
i.e. discriminant should be less than zero.

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