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

If the system of linear equations

2x + y $-$ z = 3

x $-$ y $-$ z = $\alpha$

3x + 3y + $\beta$z = 3

has infinitely many solution, then $\alpha$ + $\beta$ $-$ $\alpha$$\beta$ is equal to _____________.

Answer (integer) 5

Solution

2 $\times$ (i) $-$ (ii) $-$ (iii) gives :<br><br>$-$ (1 + $\beta$)z = 3 $-$ $\alpha$<br><br>For infinitely many solution<br><br>$\beta$ + 1 = 0 = 3 $-$ $\alpha$ $\Rightarrow$ ($\alpha$, $\beta$) = (3, $-$1)<br><br>Hence, $\alpha$ + $\beta$ $-$ $\alpha$$\beta$ = 5

About this question

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

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