Checking solutions even before you have properly attempted questions will result you in feeling you know everything and go blank in the actual exams.
Always attempt the given questions on your own before doing anything.

#TODO: To explain in detail but in short.
You have to understand conceptually everything that's in your NCERT textbooks in any case, and those actually help a lot with your enginerring entrance examination so you might as well:

• Go through all the NCERT books for both your XIth and XIIth. Don't just skim through it, understand the concepts, practice the examples and try to solve the questions on your own.