EquationsMCQMTP June 22Question 1088 of 221
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Roots of the equation 2x2+3x+7=0\displaystyle 2x^2 + 3x + 7 = 0 are α\displaystyle \alpha and β\displaystyle \beta then the value of α1+β1\displaystyle \alpha^{-1} + \beta^{-1} is

Options

A2\displaystyle 2
B3/7\displaystyle 3/7
C7/2\displaystyle 7/2
D3/7\displaystyle -3/7
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Correct Answer

Option d3/7\displaystyle -3/7

All Options:

  • A2\displaystyle 2
  • B3/7\displaystyle 3/7
  • C7/2\displaystyle 7/2
  • D3/7\displaystyle -3/7

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Detailed Solution & Explanation

Given the quadratic equation:
2x2+3x+7=02x^2 + 3x + 7 = 0
Let the roots be α\displaystyle \alpha and β\displaystyle \beta.
Using Vieta's formulas:
α+β=ba=32\alpha + \beta = -\frac{b}{a} = -\frac{3}{2}
αβ=ca=72\alpha\beta = \frac{c}{a} = \frac{7}{2}

We need to find the value of α1+β1\displaystyle \alpha^{-1} + \beta^{-1}:
α1+β1=1α+1β=α+βαβ\alpha^{-1} + \beta^{-1} = \frac{1}{\alpha} + \frac{1}{\beta} = \frac{\alpha + \beta}{\alpha\beta}
Substitute the values of the sum and product:
1α+1β=3/27/2=37\frac{1}{\alpha} + \frac{1}{\beta} = \frac{-3/2}{7/2} = -\frac{3}{7}
This corresponds to 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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