sir Idont know basics for objective but i want to get free seat in jeemains so say me which books are useful for learn and archeive jeemains

First of all there are no free seats in JEE Mains. Not in the IITs or NITs or even the IIITs. So thats a myth I am sorry to say. Some states which take JEE Main scores may have tuition fee waiver seats but then those are for the students of that state only and dependent upon the annual income.

First of all use NCERT books to get the basics right. If youo know the concepts well then youo are good to go. Check the previous year question papers and start practising many times. It doesnt matter if you dont do well at the start but you should be able to catch up if you keep it up. also revise where you have gone and understand to correct it. practise and work hard to be able to do many question papers and be prepared to slog hard for hours to get it right.

All the best!