English

Nature of Roots of a Quadratic Equation

Advertisements

Topics

Estimated time: 6 minutes
Maharashtra State Board: Class 10

Introduction

Every quadratic equation has two roots, but these roots may not always be of the same type. Sometimes both roots are real and different, sometimes they are real and equal, and sometimes they are not real at all. The discriminant helps us identify the nature of these roots without actually solving the equation.

The discriminant is given by:

\[ D = b^{2} - 4ac \]

By examining whether \[ D \] is positive, zero, or negative, we can quickly decide whether a quadratic equation has:

  • Two distinct real roots
  • Two equal real roots
  • No real roots
Maharashtra State Board: Class 10

Nature of Roots

Maharashtra State Board: Class 10

Example

\[ \begin{array}{r l} \text{Question} & x^{2} + 2x - 9 = 0 \\ \text{Solution :} & \text{Compare } x^{2} + 2x - 9 = 0 \text{ with} \\ & ax^{2} + bx + c = 0. \\& a = 1,\ \ b = 2,\ \ c = -9. \\& \begin{aligned} \therefore\ b^{2} - 4ac &= 2^{2} - 4 \times 1 \times (-9) \\ D &= 4 - (-36) \\ D &= 40 \end{aligned} \\ & \therefore\ b^{2} - 4ac > 0 \\ & \therefore\ \text{the roots of the equation are real and unequal.} \end{array} \]

CBSE: Class 10
Maharashtra State Board: Class 10
CISCE: Class 10

Key Points: Nature of Roots

D = b2 – 4ac 

Condition on D Nature of Roots
(D > 0) Roots are real and unequal
(D = 0) Roots are real and equal
(D < 0) No real roots

Test Yourself

Shaalaa.com | Quadratic Equation part 10 (Quadratic Formula, Nature of roots)

Shaalaa.com


Next video


Shaalaa.com


Quadratic Equation part 10 (Quadratic Formula, Nature of roots) [00:12:47]
S
Advertisements
Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×