The quadratic equation $3 x^{2} - 12 x + 12 = 0$ has equal real roots. What is the value of its discriminant?

medium MCQ 3 marks Class 9 · Mathematics · Polynomials

Answer

The correct answer is 0 — Since the discriminant is zero, the equation has equal real roots, and $D = 0$ .

Step-by-step solution

The discriminant of $a x^{2} + b x + c$ is $D = b^{2} - 4 a c$ .
Here $a = 3$ , $b = - 12$ , $c = 12$ .
Compute $D = (- 12)^{2} - 4 \cdot 3 \cdot 12 = 144 - 144 = 0$ .
Since the discriminant is zero, the equation has equal real roots, and $D = 0$ .

Common mistake: Choosing the wrong formula for the discriminant or miscalculating the product

4 a c

Concept tested: Discriminant of quadratic with equal roots