Question

Which of the following quadratic equations has real and equal roots? 

विकल्प

• (x + 1)² = 2x + 1

• x² + x = 0

• x² − 4 = 0

• x² + x + 1 = 0

Answer 1

x² + x = 0

Explanation:

For a quadratic equation ax² + bx + c = 0 to have real and equal roots, the discriminant Δ = b² − 4ac must be zero.

Only x² + x = 0 satisfies this condition (Δ = 1² − 4(1)(0) = 1 = 0) is false correction: 1 − 0 = 1, so checking other options: 

x² − 4 = 0

⇒ Δ = 0