In an arithmetic progression, whose first term and common difference are both non-zero, Un denotes the nth term and Sn denotes the sum of n terms. If U6, U4, U10 for a geometric progression:
i) show that S10=0
ii) show that S6 + S12 = 0
iii) deduce that U7 + U8 + U9 + U10 = U11 +U12
i)...