Chapter 2 · Question 5

Form a quadratic polynomial whose zeroes are 44 and 1-1.

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Q5

Form a quadratic polynomial whose zeroes are 44 and 1-1.

Answer Revealed
Direct Answer:
A quadratic with zeroes α\alpha and β\beta is k[x2(α+β)x+αβ]k[x^2-(\alpha+\beta)x+\alpha\beta]. Taking k=1k=1, zeroes 4,14,-1 give x23x4x^2-3x-4.

Simple Explanation

Use sum =3=3 and product =4=-4. The polynomial is x23x4x^2-3x-4.

Exam-Ready Structure

Here α=4\alpha=4 and β=1\beta=-1. Sum α+β=3\alpha+\beta=3 and product αβ=4\alpha\beta=-4. A monic quadratic polynomial is x2(α+β)x+αβ=x23x4x^2-(\alpha+\beta)x+\alpha\beta=x^2-3x-4. Any non-zero multiple of this polynomial has the same zeroes.

Key Points

  • A quadratic with zeroes α\alpha and β\beta is k[x2(α+β)x+αβ]k[x^2-(\alpha+\beta)x+\alpha\beta].
  • Use the NCERT formula or theorem carefully.
  • Write units and final conclusion where applicable.