NCERT Exemplar Solutions
Class 10 - Mathematics - CHAPTER 4: Quadatric Equation - Exercise 4.2
Question 5

Question. 5

Does there exist a quadratic equation with irrational coefficients but rational roots? Why?

Answer:

Yes.

Detailed Answer with Explanation:

Let's understand step by step:

  1. A quadratic equation is in the form: \(ax^2 + bx + c = 0\), where \(a, b, c\) are called coefficients.
  2. Coefficients can be any real numbers: they may be rational (like \(2, -3, \dfrac{1}{2}\)) or irrational (like \(\sqrt{2}, \pi\)).
  3. We want to check: is it possible that the coefficients are irrational but the solutions (roots) are rational numbers?

Example:

  • Take the equation: \(\sqrt{2}x^2 - \sqrt{2} = 0\).
  • Here, the coefficient of \(x^2\) is \(\sqrt{2}\) (irrational) and the constant term is \(-\sqrt{2}\) (irrational).

Now solve it:

  1. \(\sqrt{2}x^2 - \sqrt{2} = 0\)
  2. Take out \(\sqrt{2}\) as common: \(\sqrt{2}(x^2 - 1) = 0\)
  3. So, \(x^2 - 1 = 0\)
  4. Which gives: \(x^2 = 1\)
  5. Therefore, \(x = \pm 1\)

Thus, the roots are \(1\) and \(-1\), both rational numbers.

Conclusion: Yes, it is possible. The equation \(\sqrt{2}x^2 - \sqrt{2} = 0\) has irrational coefficients but rational roots.

NCERT Exemplar Solutions Class 10 – Mathematics – CHAPTER 4: Quadatric Equation – Exercise 4.2 | Detailed Answers