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

The value of k $\in$R, for which the following system of linear equations

3x $-$ y + 4z = 3,

x + 2y $-$ 3z = $-$2

6x + 5y + kz = $-$3,

has infinitely many solutions, is :

  1. A 3
  2. B $-$5 Correct answer
  3. C 5
  4. D $-$3

Solution

$$\left| {\matrix{ 3 &amp; { - 1} &amp; 4 \cr 1 &amp; 2 &amp; { - 3} \cr 6 &amp; 5 &amp; k \cr } } \right| = 0$$<br><br>$\Rightarrow$ 3(2k + 15) + K + 18 $-$ 28 = 0<br><br>$\Rightarrow$ 7k + 35 = 0 <br><br>$\Rightarrow$ k = $-$ 5

About this question

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

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