Let a1, a2, a3, ..., a10 be an arithmetic series. If a1 + a3 = -2 and a2 + a4 + a6 = 1, then find a1.
Suppose \(d = a_2 - a_1\). Note that the given conditions are equivalent to:
\(\begin{cases} a_1 + d = -1\\ a_1 + 3d = \dfrac13 \end{cases}\)
Solving gives \(d = \dfrac23\) and \(a_1 = -\dfrac53\).
+964 
