Let $\alpha \beta \gamma=45 ; \alpha, \beta, \gamma \in \mathbb{R}$. If $x(\alpha, 1,2)+y(1, \beta, 2)+z(2,3…

Let $\alpha \beta \gamma=45 ; \alpha, \beta, \gamma \in \mathbb{R}$. If $x(\alpha, 1,2)+y(1, \beta, 2)+z(2,3, \gamma)=(0,0,0)$ for some $x, y, z \in \mathbb{R}, x y z \neq 0$, then $6 \alpha+4 \beta+\gamma$ is equal to _______

Solution

$\begin{aligned} & \alpha \beta \gamma=45, \alpha \beta \gamma \in \mathrm{R} \\ & \mathrm{x}(\alpha, 1,2)+\mathrm{y}(1, \beta, 2)+\mathrm{z}(2,3, \gamma)=(0,0,0) \\ & \mathrm{x}, \mathrm{y}, \mathrm{z} \in \mathrm{R}, \mathrm{xyz} \neq 0 \\ & \alpha \mathrm{x}+\mathrm{y}+2 \mathrm{z}=0 \\ & \mathrm{x}+\beta \mathrm{y}+3 \mathrm{z}=0 \\ & 2 \mathrm{x}+2 \mathrm{y}+\gamma \mathrm{z}=0 \\ & \mathrm{xyz} \neq 0 \Rightarrow \text { non-trivial } \\ & \left|\begin{array}{lll}\alpha & 1 & 2 \\ 1 & \beta & 3 \\ 2 & 2 & \gamma\end{array}\right|=0\end{aligned}$ $\begin{aligned} & \Rightarrow \alpha(\beta \gamma-6)-1(\gamma-6)+2(2-2 \beta)=0 \\ & \Rightarrow \alpha \beta \gamma-6 \alpha-\gamma+6+4-4 \beta=0 \\ & \Rightarrow 6 \alpha+4 \beta+\gamma=55\end{aligned}$

Asked in: JEE Main 2024 (06 Apr Shift 1)

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