JEE Main 2021 (Online) 3rd August Evening ShiftQuestion 1
A plane intersects the $yz$-plane at $x=0$, $2y-3z=5$ and it intersects the $xy$-plane at $z=0$, $7x+4y=10$. Then the distance of the point $(1,-2,-1)$ from this plane is
3D Geometry
Solution
Plane $7x+4y+cz=d$; at $x=0$: $4y+cz=d\propto2y-3z=5$ gives $c=-6$, $d=10$. Plane $7x+4y-6z=10$. Distance of $(1,-2,-1)$: $\frac{|7-8+6-10|}{\sqrt{101}}=\frac5{\sqrt{101}}$.