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 :
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
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