1. Find the first three terms of the arithmetic series. Remember to use the formula S, - (a₁ + a) to find n, and the formula a, = a₁ + (n-1)d to find d.
a₁-10, a, -26, S, - 80
26 +22+18+...
O-10+16+42+...
O-10+-14+-18+....
O-10+-6+-2+...