Arithmetic & Geometric Sequence Anatomy

a sub n variable

Term to be found

a sub k

Any term

d

Common difference

n

Term Number of Number to be Found (order of it)

k

Term number of known/given term

r

Common ratio

Arithmetic Sequence Similar Behaviors

Behave like linear functions, but aren’t continuous

Arithmetic Sequence Formula

a sub n = (a sub 1) + d(n - 1)

Moving Back Terms in Arithmetic Sequences

Flip sign to negative

Geometric Sequence Formula

a sub n = a sub 1 * r^n-1

Finding a Geometric Sequence with Two Non-Consecutive Terms

Set up incomplete equations for both, divide 1st on top of 2nd equation, then solve for r and find first term.