JEE Main 2021 (Online) 27th August Evening ShiftQuestion 1
The equation of the plane passing through the line of intersection of the planes $\vec{r}\cdot\left(\hat{i}+\hat{j}+\hat{k}\right)=1$ and $\vec{r}\cdot\left(2\hat{i}+3\hat{j}-\hat{k}\right)+4=0$ and parallel to the $x$-axis is :
3D Geometry
Solution
Plane $(x+y+z-1)+\lambda(2x+3y-z+4)=0$ parallel to $x$-axis: coefficient of $x$ is $1+2\lambda=0$, $\lambda=-\frac12$, giving $-y+3z-6=0$, i.e. $\vec r\cdot(\hat j-3\hat k)+6=0$.