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These are some important chapters:
Mathematics:

• Complex Number , Quadratic Equations
• Coordinate Geometry (straight line, circle and conic section )
• Calculus ( function, application of derivatives, definite integration are most important part in calculus )
• 3-D and vector
• Bionomial theoem and Sequences and Series

Chemistry

• Chemical Bonding and Molecular Structure
• Chemical Thermodynamics
• Electrochemistry
• Inorganic Chemistry ( most important part for jee main )
• Organic Chemistry( xiith class oganic chemisty is more imporant,full scoring )
• Polymers and Bio Molecules
• Environmental Chemistry
• Chemistry in Everyday Life

Physics

• Electrostatics
• Current Electricity
• Magnetic Effects of Current and Magnetism
• Electromagnetic Induction and Alternating Currents
• Optics
• Dual Nature of Matter and Radiation,Atoms and Nuclei
• Thermodynamics
• Oscillations and Wave

All the best:)

Hii

As such this can not be predicted because we dont know from where the question can be put up. But with the hep of previous trends we have made the syllabus and chapterwise weightage of JEE mains which you find find from the link below.
https://engineering.careers360.com/articles/jee-main-syllabus-weightage

Thanks!!