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COMPLEX NUMBERS AND QUADRATIC EQUATIONS — MATHS STD 11 Science — Question

Gujarat 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
  1. less than zero
Solution:
For a quadratic equation, $a x^2+b x+c=0$, discriminant is $b^2-4 a c$.
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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