ICSEClass XMathematicsQuadratic Equations01 Mark2024 Easy

QQuestion

The roots of the equation px² − qx + r = 0 are real and equal if:

(a) p² = 4qr

(b) q² = 4pr

(c) −q² = 4pr

(d) p² > 4qr

Exam-ready answer 01 Mark

Answer

(b) q² = 4pr

Explanation:

For a quadratic equation ax² + bx + c = 0, the roots are real and equal when the discriminant is zero.

D = b² − 4ac

Here, a = p, b = −q and c = r.

Therefore,

D = (−q)² − 4pr

⇒ D = q² − 4pr

For equal roots:

q² − 4pr = 0

⇒ q² = 4pr

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