Analyzing the Setup
Imagine you are standing in the vast expanse of 3D space. You have a point P(3,2,0) and a line L defined by the symmetric equations:
The standard, textbook approach is to find the normal vector of the plane by taking the cross product of the line's direction vector and the vector connecting the point to the line.
However, in the world of JEE Advanced, the most dangerous assumption is that the geometry is 'standard.' If the point P is actually sitting right on the line L, the line and the point would not define a unique plane. Instead, they would act like the spine of a book, with infinitely many planes passing through them.
The Investigation
Testing the Reality
Let us test our hypothesis by substituting the coordinates of P(3,2,0) into the line equation:
Calculating these ratios, we get:
The ratios are identical! This is a massive revelation: our point P lies exactly on the line L. We are not looking for a unique plane; we are looking for one specific plane out of an infinite family that contains this line.
The Strategy
The Power of Verification
Since we cannot derive a single equation from scratch, we must pivot. We know that the correct plane must contain the entire line L.
A plane contains a line if and only if it contains at least two distinct points on that line. We already have point P(3,2,0). We need a second point.
Looking at the line equation, we can easily extract the base point A(4,7,4). Now, we simply test the options provided.
Final Verification
Let us check the option x−y+z=1. Substituting P(3,2,0), we get:
It works! Now, we must verify with point A(4,7,4):
Both points satisfy the equation. Because this plane contains two distinct points of the line, it must contain the entire line itself.
The mystery is solved, not by brute-force calculation, but by conceptual insight and strategic verification. Keep this in your toolkit: always check if your point lies on the line before you start your cross products!