Let λ be a real number for which the system of linear equations

Question:

Let $\lambda$ be a real number for which the system of linear equations

$x+y+z=6$

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

$3 x+2 y-4 z=-5$

has infinitely many solutions. Then $\lambda$ is a root of the quadratic equation.

  1. $\lambda^{2}-3 \lambda-4=0$

  2. $\lambda^{2}-\lambda-6=0$

  3. $\lambda^{2}+3 \lambda-4=0$

  4. $\lambda^{2}+\lambda-6=0$


Correct Option: , 2

Solution:

$\mathrm{D}=0$

$\left|\begin{array}{ccc}1 & 1 & 1 \\ 4 & \lambda & -\lambda \\ 3 & 2 & -4\end{array}\right|=0 \Rightarrow \lambda=3$

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