[Solved] Let a_1, a_2, a_3, ...., a_{11} be real numbers satisfying a_1 = 15, 27 - 2a_2 > 0 and a_k = 2a_{k-1} - a_{k-2}, for k = 3, 4, ...., 11. If \\frac{a_{1}^{2} + a_{2}^{2} + ..... + a_{11}^{2}}{11} = 90, then the value of \\frac{a_1 + a_2 + .... + a_{11}}{11} is equal to - - JEE (Advanced) 2010 Paper-2