Let a1, a2, a3, ..., a10 be an arithmetic series. If a1 + a3 = -2 and a2 + a4 + a6 = 1, then find a1.
Suppose d=a2−a1. Note that the given conditions are equivalent to:
{a1+d=−1a1+3d=13
Solving gives d=23 and a1=−53.