The secret was nothing but thinking mathematically . In the questions which are really complex   first we  need to simplify the equations. In part b of question 2 , the answer was very simple but the only thing we need to do was to cancel some terms . There were two terms (4^n) and (2^2n) we just need to think that these are equal by doing some algebra , then we can cancel these both. There is one important thing in math that it is not important to know the answer of the problem , but the solution is really important so that one has to prove himself that solution is correct.