How many real roots does x² − 6x + 9 = 0 have?

How many real roots does $x^{2} - 6 x + 9 = 0$ have?

Class 10Quadratic EquationsAlgebra — Quadratics

D = 36 - 36 = 0

, so the roots are equal. There is one distinct real root,

x = 3

(a repeated root).

Answer: A) 1

D = b^{2} - 4 a c

classifies the roots of

a x^{2} + b x + c = 0 : - * * D > 0

**: TWO distinct real roots. Parabola crosses

x

-axis at two points.
- **

D = 0

**: ONE repeated real root (called a 'double root' or 'two equal roots'). Parabola touches

x

-axis at the vertex.
- **

D < 0

**: NO real roots. Parabola does not touch the

x

-axis at all.

**Use case**: 'For what values of

k

does

k x^{2} + 2 x + 1 = 0

have equal roots?' → set

D = 0 : 4 - 4 k = 0

→

k = 1

.

You can answer 'how many real roots?' WITHOUT computing them — just compute

D

Don't just memorise the answer — build a daily practice habit.