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NCERT Solutions for Class 10 Maths Chapter 4 Quadratic Equations

NCERT Solutions for Class 10 Maths Chapter 4 Quadratic Equations covers the standard form of a quadratic equation, solving by factorisation, completing the square, the quadratic formula, and the nature of roots using the discriminant.

Overview of Topics & Subtopics (Click to Jump)

1. Quadratic Equations

Short Note:

• A quadratic equation in x is an equation of the form ax² + bx + c = 0, where a, b, c are real numbers and a ≠ 0.

• A real number α is a root of the quadratic equation if aα² + bα + c = 0; the roots are the same as the zeroes of the corresponding quadratic polynomial.

2. Solution by Factorisation

Short Note:

• If ax²+bx+c can be written as a product of two linear factors, the roots can be found by setting each factor to zero.

3. Solution by Completing the Square & the Quadratic Formula

Short Note:

• Every quadratic equation can be solved by completing the square to express it as (x + k)² = constant.

• Quadratic Formula: For ax²+bx+c=0 (a ≠ 0), x = [−b ± √(b²−4ac)] / 2a.

4. Nature of Roots (Discriminant)

Short Note:

• The discriminant D = b² − 4ac determines the nature of the roots.

• If D > 0: two distinct real roots. If D = 0: two equal real roots. If D < 0: no real roots.

NCERT Textbook Exercise Questions

Find the roots of the quadratic equation 2x² − 5x + 3 = 0 by factorisation.
Answer: 2x² − 5x + 3 = 2x² − 2x − 3x + 3 = 2x(x−1) − 3(x−1) = (x−1)(2x−3). Setting each factor to zero: x = 1 or x = 3/2.
Find the roots of 2x² − 7x + 3 = 0 using the quadratic formula.
Answer: Here a=2, b=−7, c=3. D = 49−24 = 25. x = [7 ± 5]/4, giving x = 3 or x = 1/2.
Find the discriminant of the equation 2x² − 4x + 3 = 0 and hence find the nature of its roots.
Answer: D = (−4)² − 4(2)(3) = 16 − 24 = −8. Since D < 0, the equation has no real roots.
Find the values of k for which the equation kx² − 6x − 2 = 0 has two equal roots.
Answer: This is quadratic only if k ≠ 0. For equal roots, D = 0: (−6)² − 4(k)(−2) = 0 ⇒ 36 + 8k = 0 ⇒ k = −9/2.
The product of two consecutive positive integers is 306. Find the integers using a quadratic equation.
Answer: Let the integers be x and x+1. x(x+1) = 306 ⇒ x²+x−306=0. Factorising: (x−17)(x+18)=0 ⇒ x=17 (rejecting negative root). So the integers are 17 and 18.
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Class 10 › Mathematics › Quadratic Equations
Chapter notesRead the chapterPractice MCQsCheck what you rememberChapter test10 questions on one pageOnline testTest 1, 2 and 3, one question at a timePYQPrevious year questionsStudy materialPDF notes
Topics in this chapter: Quadratic EquationsSolution by FactorisationSolution by Completing the Square & the Quadratic FormulaNature of Roots (Discriminant)