A planet moving around sun sweeps area A1 in 2 days, A2 in 3 days and A3 in 6 days. Then the relation between A1,A2 and A3 is:
If a1,a2,a3,a4 are the coefficients of any four
consecutive terms in the expansion of (1+x)n, then
a1a1+a2 + a3a3+a4 =