Sequence Sums

Before summing a sequence, first identify its type:

• Arithmetic (constant difference): S_n = n/2 × (2a + (n−1)d)
• Geometric (constant ratio): S_n = a(rⁿ−1)/(r−1)

Using the wrong formula for the wrong type of sequence is a common mistake — always check the pattern of differences or ratios first.

Identify a sequence's type, then compute its sum using the correct formula.

Continue exploring related topics:

• Arithmetic Sequences - nth Term and Sum
• Geometric Sequences - Common Ratio and Exponential Growth
• Infinite Geometric Series - Sum to Infinity