Hey,
In JEE-Mains examination, straight line and circles form the root of coordinate geometry.
The Straight line forms the basis of coordinate geometry, also covers almost 20% of JEE Advanced paper. You need to know about section formula, the distance between two points if coordinates are given and various other fundamentals for solving straight line questions. The important topic from straight lines are:
1. The position of a point w.r.t. line
2. Image of a point in a line
3. Foot of perpendicular
4. Angle Bisector
5. Rotation of line
Also, you need to have knowledge about a straight line for learning circles. The circle is another important topic in coordinate geometry. With little hard work, it paves the path to solve difficult problems also. The important topics to study in circles are:
1. General Equation of Circle
2. Director Circle
3. Parametric Form
4. Radical Axis and Radical Center
5. Straight line and Circle problems
These are the important topic which you must practice. Also, solve practice papers and previous year exam to analyze the pattern of examination.
All the Best!