Let a_{1},a_{2},a_{3},. be in an arithmetic progression of positive terms. Let A_{k} = a_{1}^{2} - a_{2}^{2} + a_{3}^{2} - a_{4}^{2} + .. + a_{2k - 1}^{2} - a_{2k}^{2}. If A_{3} = - 153,A_{5} = - 435 and a_{1}^{2} + a_{2}^{2} + a_{3}^{2} = 66, then a_{17} - A_{7} is equal to : Sequence & Series (Mathematics) | DivineJEE