Patterns and Sequences
Sequence Sums
Before summing a sequence, first identify its type:
- Arithmetic (constant difference): Sn = n/2 × (2a + (n−1)d)
- Geometric (constant ratio): Sn = 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.
Practice: Sequence Sums
Identify a sequence's type, then compute its sum using the correct formula.