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Introduction

Dive into the fascinating world of quadratic equations, where numbers and variables dance together to form equations with a touch of elegance! In this chapter, you'll explore equations where the highest power of the variable is two. From understanding their standard form to solving them with various methods, quadratic equations are like puzzles waiting to be solved. Get ready to master the art of finding solutions and discovering the nature of roots!

Quadratic Equations Chapter Notes | Mathematics Class 10 ICSE

  • A quadratic equation is an equation with one variable where the highest power is two.
  • It is written in the form ax2 + bx + c = 0, where a, b, and c are real numbers, and a ≠ 0.
  • Every quadratic equation has two solutions, known as roots.
  • The expression b2 - 4ac is called the discriminant, denoted by D.
  • Discriminant formula: D = b2 - 4ac.
  • An adfected quadratic equation has a square term and a linear term, e.g., 4x2 + 5x = 0.
  • A pure quadratic equation has only the square term, e.g., x2 = 4.

Example: 3x2 + 4x + 7 = 0 is a quadratic equation because the highest power of x is 2.

To Examine the Nature of the Roots

  • The nature of roots (real, imaginary, equal, or unequal) depends on the discriminant D = b2 - 4ac.

Quadratic Equations Chapter Notes | Mathematics Class 10 ICSE

  • Every rational and irrational number is a real number.
  • The square root of a negative number is imaginary, e.g., √(-4) is imaginary.

Example 1: For 5x2 - 6x + 7 = 0, 

a = 5, b = -6, c = 7.

Discriminant D = (-6)2 - 4 × 5 × 7 = 36 - 140 = -104. 

Since D < 0, the roots are imaginary.

Example 2: Find the value of m if the roots of (4 + m)x2 + (m + 1)x + 1 = 0 are equal.

  • Identify a = 4 + m, b = m + 1, c = 1.
  • For equal roots, D = 0, so b2 - 4ac = 0.
  • Calculate: (m + 1)2 - 4(4 + m) × 1 = 0.
  • Expand: m2 + 2m + 1 - 16 - 4m = 0.
  • Simplify: m2 - 2m - 15 = 0.
  • Solve: (m - 5)(m + 3) = 0, so m = 5 or m = -3.

Solving Quadratic Equations by Factorisation

  • Steps to solve by factorisation:
  • Remove fractions and brackets if present.
  • Rearrange to the form ax2 + bx + c = 0.
  • Factorise the left-hand side.
  • Use the Zero Product Rule: If (p)(q) = 0, then p = 0 or q = 0.
  • Solve each factor to find the roots.

Example 1: Solve 2x2 - 7x = 39.

  • Rearrange: 2x2 - 7x - 39 = 0.
  • Factorise: 2x2 - 13x + 6x - 39 = x(2x - 13) + 3(2x - 13) = (2x - 13)(x + 3) = 0.
  • Apply Zero Product Rule: 2x - 13 = 0 or x + 3 = 0.
  • Solve: x = 13/2 or x = -3.

Example 2: Solve x/(x - 1) + (x - 1)/x = 5/2.

  • Combine fractions: [x2 + (x - 1)2] / [x(x - 1)] = 5/2.
  • Simplify numerator: x2 + x2 - 2x + 1 = 2x2 - 2x + 1.
  • Cross-multiply: 2(2x2 - 2x + 1) = 5(x2 - x).
  • Expand: 4x2 - 4x + 2 = 5x2 - 5x.
  • Rearrange: -x2 + x + 2 = 0, or x2 - x - 2 = 0.
  • Factorise: (x - 2)(x + 1) = 0.
  • Solve: x = 2 or x = -1.

Solving Quadratic Equations Using the Formula

  • The quadratic formula for ax2 + bx + c = 0 is:

Quadratic Equations Chapter Notes | Mathematics Class 10 ICSE

Steps to use the formula:

  • Identify a, b, and c from the equation.
  • Calculate the discriminant: b2 - 4ac.
  • Substitute into the formula to find x.
  • Simplify the expression to get the roots.

Example 1: Solve 5x2 - 2x - 3 = 0.

  • Identify: a = 5, b = -2, c = -3.
  • Discriminant: (-2)2 - 4 × 5 × (-3) = 4 + 60 = 64.
  • Apply formula: x = [2 ± √64] / (2 × 5) = [2 ± 8] / 10.
  • Solve: x = (2 + 8)/10 = 1 or x = (2 - 8)/10 = -3/5.

Example 2: Solve x2 - 10x + 6 = 0, correct to 2 decimal places.

  • Identify: a = 1, b = -10, c = 6.
  • Discriminant: (-10)2 - 4 × 1 × 6 = 100 - 24 = 76.
  • √76 ≈ 8.718.
  • Apply formula: x = [10 ± 8.718] / 2.
  • Solve: x = (10 + 8.718)/2 = 9.359 ≈ 9.36 or x = (10 - 8.718)/2 = 0.641 ≈ 0.64.

Equations Reducible to Quadratic Equations

  • Some equations can be transformed into quadratic equations by substitution.
  • Identify a substitution that simplifies the equation to ax2 + bx + c = 0.
  • Solve the resulting quadratic equation.
  • Back-substitute to find the original variable.

Example 1: Solve 2x4 - 5x2 + 3 = 0.

  • Substitute y = x2, so 2y2 - 5y + 3 = 0.
  • Factorise: (y - 1)(2y - 3) = 0.
  • Solve: y = 1 or y = 3/2.
  • Back-substitute: If y = 1, x2 = 1, x = ±1. 
  • If y = 3/2, x2 = 3/2, x = ±√(3/2) = ±√6/2.

Example 2: Solve √(x/(1 - x)) + √((1 - x)/x) = 13/6, x ≠ 0, x ≠ 1.

  • Let √(x/(1 - x)) = y, so √((1 - x)/x) = 1/y.
  • Equation becomes: y + 1/y = 13/6.
  • Multiply through by y: y2 + 1 = (13/6)y.
  • Rearrange: 6y2 - 13y + 6 = 0.
  • Factorise: (2y - 3)(3y - 2) = 0, so y = 3/2 or y = 2/3.
  • For y = 3/2: √(x/(1 - x)) = 3/2, so x/(1 - x) = 9/4, solve to get x = 9/13.
  • For y = 2/3: √(x/(1 - x)) = 2/3, so x/(1 - x) = 4/9, solve to get x = 4/13.

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FAQs on Quadratic Equations Chapter Notes - Mathematics Class 10 ICSE

1. What are the different methods to solve quadratic equations?
Ans. Quadratic equations can be solved using several methods, including factorization, completing the square, and the quadratic formula. Factorization involves expressing the equation in a product form, while completing the square rewrites it in a perfect square format. The quadratic formula, x = (-b ± √(b² - 4ac)) / 2a, is a universal method applicable to all quadratic equations.
2. How can we examine the nature of the roots of a quadratic equation?
Ans. The nature of the roots of a quadratic equation can be determined using the discriminant, which is given by the expression b² - 4ac. If the discriminant is positive, the equation has two distinct real roots. If it is zero, there is one real root (a repeated root). If the discriminant is negative, the roots are complex and not real.
3. What is the significance of the quadratic formula in solving equations?
Ans. The quadratic formula is significant because it provides a reliable method to find the roots of any quadratic equation, regardless of whether it can be factored easily. This formula ensures that all possible roots (real or complex) can be calculated, making it a powerful tool in algebra.
4. What are equations reducible to quadratic equations, and how can they be solved?
Ans. Equations reducible to quadratic equations are those that can be transformed into a standard quadratic form, often through substitution or rearrangement. For example, equations involving variables raised to higher powers or certain polynomial forms can be simplified into a quadratic equation, allowing the use of standard solving techniques.
5. Why is factorization an important method for solving quadratic equations?
Ans. Factorization is important because it allows for a straightforward way to solve quadratic equations, especially when the roots are rational numbers. It simplifies the process of finding the roots by breaking down the quadratic into simpler binomials, making it easier to analyze and understand the behavior of the equation.
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