EquationsMCQPYQ June 24Question 1110 of 221
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The equation x33x24x+12=0\displaystyle x^3 - 3x^2 - 4x + 12 = 0 has three real roots. They are:

Options

A2,2,3\displaystyle -2, 2, 3
B2,2,3\displaystyle -2, 2, -3
C2,2,3\displaystyle 2, -2, -3
D2,2,3\displaystyle 2, -2, 3
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Correct Answer

Option a2,2,3\displaystyle -2, 2, 3

All Options:

  • A2,2,3\displaystyle -2, 2, 3
  • B2,2,3\displaystyle -2, 2, -3
  • C2,2,3\displaystyle 2, -2, -3
  • D2,2,3\displaystyle 2, -2, 3

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Detailed Solution & Explanation

Let us solve the cubic equation x33x24x+12=0\displaystyle x^3 - 3x^2 - 4x + 12 = 0 by factoring by grouping:
x33x24x+12=0x^3 - 3x^2 - 4x + 12 = 0
x2(x3)4(x3)=0x^2(x - 3) - 4(x - 3) = 0
(x24)(x3)=0(x^2 - 4)(x - 3) = 0
(x2)(x+2)(x3)=0(x - 2)(x + 2)(x - 3) = 0

This gives the three roots:
x2=0    x=2\displaystyle x - 2 = 0 \implies x = 2
x+2=0    x=2\displaystyle x + 2 = 0 \implies x = -2
x3=0    x=3\displaystyle x - 3 = 0 \implies x = 3

Thus, the roots are 2,2,3\displaystyle -2, 2, 3, which are listed in both Option (a) and Option (d). Since the order of roots does not affect the set of solutions, both options represent the mathematically correct set of roots, with Option (a) being the officially designated answer.

Hence, the correct option is **Option (a)**.

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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