If equation of the plane that contains the point $(-2,3,5)$ and is perpendicular to each of the planes $2 x+4 y+5 z=8$ and $3 x-2 y+3 z=5$ is $\alpha x+\beta y+\gamma z+97=0$ then $\alpha+\beta+\gamma=$
Solution
The equation of plane that passes through the point $(-2,3,5)$ is
<br/><br/>$a(x+2)+b(y-3)+c(z-5)=0$ ..........(i)
<br/><br/>The plane is perpendicular to
<br/><br/>$$
\begin{array}{ll}
2 x+4 y+5 z =8 \text { and } 3 x-2 y+3 z=5 \\\\
\end{array}
$$
<br/><br/>$$
\begin{array}{ll}
\therefore 2 a+4 b+5 c=0 ..........(ii)\\\\
\text { and } 3 a-2 b+3 c=0 ..........(iii)
\end{array}
$$
<br/><br/>$$
\begin{aligned}
& \therefore \quad \frac{\mathrm{a}}{\left|\begin{array}{cc}
4 & 5 \\
-2 & 3
\end{array}\right|}=\frac{-\mathrm{b}}{\left|\begin{array}{ll}
2 & 5 \\
3 & 3
\end{array}\right|}=\frac{\mathrm{c}}{\left|\begin{array}{cc}
2 & 4 \\
3 & -2
\end{array}\right|} \\\\
& \Rightarrow \frac{\mathrm{a}}{22}=\frac{\mathrm{b}}{9}=\frac{\mathrm{c}}{-16}
\end{aligned}
$$
<br/><br/>$\therefore$ From Equation (i)
equation of plane
<br/><br/>$$
\begin{aligned}
&22(x+2)+9(y-3)-16(z-5)=0 \\\\
&\Rightarrow 22 x+9 y-16 z+97=0
\end{aligned}
$$
<br/><br/>Here, $\alpha=22, \beta=9, \gamma=-16$
<br/><br/>$\therefore \alpha+\beta+\gamma=22+9-16=15$
About this question
Subject: Mathematics · Chapter: Three Dimensional Geometry · Topic: Direction Cosines and Ratios
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