1. The problem statement, all variables and given/known data Consider any sequence a1, a2,..., an and the nxn array of values bij = aiaj. Which terms in the array are involved in the sums L = Ʃ(between i=1 and n)Ʃ(between j=1 and i) bij and U = Ʃ(between j=1 and n)Ʃ(between i=1 and j) bij? Also, by symmetry, show that L=U. 2. Relevant equations n/a 3. The attempt at a solution I've just started this topic and the double summation is really confusing me. Any guidance or suggestions on how to approach this would be really useful thanks.