question_answer

If the sum of the coefficients of all even powers of x in the product \[\left( 1+x+{{x}^{2}}+...+{{x}^{2n}} \right)\left( 1-x+{{x}^{2}}-{{x}^{3}}+...+{{x}^{2n}} \right)\] is 61, then n is equal to________.                                                 [JEE MAIN Held on 07-01-2020 Morning]

Answer:

30