Math 1 · Unit 9 · Lesson 1 · part 4 of 5
Some lists are neither
Not every list adds or multiplies.
Some lists are neither
Not every list adds or multiplies. These are sequences too, because each position still has exactly one term.
The square numbers
1, 4, 9, 16, 25, ...
The differences are 3, 5, 7, 9: not the same. The ratios are 4, 2.25, 1.78: not the same. Neither arithmetic nor geometric. Each term is its position times itself.
The Fibonacci numbers
0, 1, 1, 2, 3, 5, 8, 13, ...
Each term is the sum of the two before it. Again neither family, and you will meet this one again in Lesson 4.
This unit focuses on the two kinds that match our families. To tell which kind a list is, use the Unit 7, Lesson 5 check: subtract each term from the next, then divide if you need to.