Medium MCQ +4 / -1 PYQ · JEE Mains 2021

Let the system of linear equations

4x + $\lambda$y + 2z = 0

2x $-$ y + z = 0

$\mu$x + 2y + 3z = 0, $\lambda$, $\mu$$\in$R.

has a non-trivial solution. Then which of the following is true?

  1. A $\mu$ = 6, $\lambda$$\in$R Correct answer
  2. B $\lambda$ = 3, $\mu$$\in$R
  3. C $\mu$ = $-$6, $\lambda$$\in$R
  4. D $\lambda$ = 2, $\mu$$\in$R

Solution

<p>Given, system of linear equations</p> <p>4x + $\lambda$y + 2z = 0</p> <p>2x $-$ y + z = 0</p> <p>$\mu$x + 2y + 3z = 0</p> <p>For non-trivial solution, $\Delta$ = 0</p> <p>$$\left| {\matrix{ 4 & \lambda & 2 \cr 2 & { - 1} & 1 \cr \mu & 2 & 3 \cr } } \right| = 0$$</p> <p>$\Rightarrow 4( - 3 - 2) - \lambda (6 - \mu ) + 2(4 + \mu ) = 0$</p> <p>$\Rightarrow - \lambda (6 - \mu ) - 2(6 - \mu ) = 0$</p> <p>$\Rightarrow (6 - \mu )(\lambda + 2) = 0$</p> <p>$\Rightarrow \lambda = - 2$ and $\mu \in R$ or $\mu$ = 6 and $\lambda \in R$.</p>

About this question

Subject: Mathematics · Chapter: Matrices and Determinants · Topic: Types of Matrices and Operations

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