EquationsMCQPYQ Dec 23Question 1063 of 221
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If α,β\displaystyle \alpha, \beta are the roots of the equation x24x+1=0\displaystyle x^2 - 4x + 1 = 0, then value of α3+β3\displaystyle \alpha^3 + \beta^3 will be

Options

A-76
B76
C-52
D52
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Correct Answer

Option d52

All Options:

  • A-76
  • B76
  • C-52
  • D52

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Detailed Solution & Explanation

Given the quadratic equation:
x24x+1=0x^2 - 4x + 1 = 0
Using Vieta's formulas:
Sum of roots: α+β=4\displaystyle \alpha + \beta = 4
Product of roots: αβ=1\displaystyle \alpha\beta = 1

We need to find the value of α3+β3\displaystyle \alpha^3 + \beta^3. We use the identity:
α3+β3=(α+β)33αβ(α+β)\alpha^3 + \beta^3 = (\alpha + \beta)^3 - 3\alpha\beta(\alpha + \beta)
Substitute the sum and product:
α3+β3=(4)33(1)(4)\alpha^3 + \beta^3 = (4)^3 - 3(1)(4)
α3+β3=6412=52\alpha^3 + \beta^3 = 64 - 12 = 52
Therefore, the value of α3+β3\displaystyle \alpha^3 + \beta^3 is 52\displaystyle 52, which matches Option d.

*Note:* A common sign error in the formula, i.e., using +3αβ(α+β)\displaystyle +3\alpha\beta(\alpha+\beta), leads to 64+12=76\displaystyle 64 + 12 = 76 (Option b). The mathematically correct answer is 52\displaystyle 52 (Option d).
**Option d**

About This Chapter: Equations

Paper

Paper 3: Quantitative Aptitude

Weightage

4-6 Marks

Key Topics

Linear, Quadratic and Cubic Equations

This chapter covers Linear, Quadratic and Cubic Equations and is part of Paper 3: Quantitative Aptitude in the CA Foundation exam.

View Official ICAI Syllabus

Exam Strategy Tip

This topic carries 4-6 Marks weightage. Focus on understanding core concepts rather than memorizing.

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