Medium MCQ +4 / -1 PYQ · JEE Mains 2023

For $\alpha, \beta \in \mathbb{R}$, suppose the system of linear equations

$$ \begin{aligned} & x-y+z=5 \\ & 2 x+2 y+\alpha z=8 \\ & 3 x-y+4 z=\beta \end{aligned} $$

has infinitely many solutions. Then $\alpha$ and $\beta$ are the roots of :

  1. A $x^2+18 x+56=0$
  2. B $x^2-10 x+16=0$
  3. C $x^2+14 x+24=0$
  4. D $x^2-18 x+56=0$ Correct answer

Solution

<p>$$\Delta = \left| {\matrix{ 1 & { - 1} & 1 \cr 2 & 2 & \alpha \cr 3 & { - 1} & 4 \cr } } \right| = 0$$</p> <p>$\Rightarrow \alpha = 4$</p> <p>${\Delta _3} = 0$</p> <p>$$ = \left| {\matrix{ 1 & { - 1} & 5 \cr 2 & 2 & 8 \cr 3 & { - 1} & \beta \cr } } \right| = 0$$</p> <p>$\Rightarrow \beta = 14$</p> <p>$\therefore$ ${x^2} - 18x + 56 = 0$</p>

About this question

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

This question is part of PrepWiser's free JEE Main question bank. 274 more solved questions on Matrices and Determinants are available — start with the harder ones if your accuracy is >70%.

Drill 25 more like these. Every day. Free.

PrepWiser turns these solved questions into a daily practice loop. Chapter-wise drills, full mocks, AI doubt chat. No auto-renew.

Start free →