Educator

Geometric Series

• There are 2 formulas for the sum. Use one if you are given n. Use the other if you are given a_n. In both cases, you will be given the values of r and a₁.

• To find a particular term of a series, say the 4^th term, you first need to find the first term using the formula for S_n. Then multiply the first term by r³, using the formula for the nth term of a series, a_n = a₁r^n-1.