High School

Sort the sequences according to whether they are arithmetic, geometric, or neither.

1. [tex]98.3, 94.1, 89.9, 85.7, \ldots[/tex]
2. [tex]1, 0, -1, 0, \ldots[/tex]
3. [tex]1.75, 3.5, 7, 14[/tex]
4. [tex]-12, -10.8, -9.6, -8.4[/tex]
5. [tex]-1, 1, -1, 1, \ldots[/tex]

Answer :

Certainly! Let's analyze each sequence to determine whether it is arithmetic, geometric, or neither:

1. Sequence 1: [tex]\(98.3, 94.1, 89.9, 85.7, \ldots\)[/tex]

- Arithmetic Check: We find the differences between consecutive terms:
- [tex]\(94.1 - 98.3 = -4.2\)[/tex]
- [tex]\(89.9 - 94.1 = -4.2\)[/tex]
- [tex]\(85.7 - 89.9 = -4.2\)[/tex]

Since the differences are the same, this sequence is arithmetic.

2. Sequence 2: [tex]\(1, 0, -1, 0, \ldots\)[/tex]

- Arithmetic Check: Differences between consecutive terms:
- [tex]\(0 - 1 = -1\)[/tex]
- [tex]\(-1 - 0 = -1\)[/tex]
- [tex]\(0 - (-1) = 1\)[/tex]

- Geometric Check: Ratios are not consistent and the sequence repeats values, suggesting it is neither arithmetic nor geometric. This is an example of neither.

3. Sequence 3: [tex]\(1.75, 3.5, 7, 14, \ldots\)[/tex]

- Geometric Check: Ratios between consecutive terms:
- [tex]\(3.5 / 1.75 = 2\)[/tex]
- [tex]\(7 / 3.5 = 2\)[/tex]
- [tex]\(14 / 7 = 2\)[/tex]

Since the ratios are consistent, this sequence is geometric.

4. Sequence 4: [tex]\(-12, -10.8, -9.6, -8.4, \ldots\)[/tex]

- Arithmetic Check: Differences between consecutive terms:
- [tex]\(-10.8 - (-12) = 1.2\)[/tex]
- [tex]\(-9.6 - (-10.8) = 1.2\)[/tex]
- [tex]\(-8.4 - (-9.6) = 1.2\)[/tex]

Since the differences are the same, this sequence is arithmetic.

5. Sequence 5: [tex]\(-1, 1, -1, 1, \ldots\)[/tex]

- Arithmetic Check: Differences alternate:
- [tex]\(1 - (-1) = 2\)[/tex]
- [tex]\(-1 - 1 = -2\)[/tex]
- [tex]\(1 - (-1) = 2\)[/tex]

- Geometric Check: Ratios alternate:
- [tex]\(1 / (-1) = -1\)[/tex]
- [tex]\(-1 / 1 = -1\)[/tex]
- [tex]\(1 / (-1) = -1\)[/tex]

This sequence alternates signs but maintains a consistent ratio, hence it can be considered geometric with a common ratio of [tex]\(-1\)[/tex].

In summary, the sequences are classified as follows:

- Sequence 1: Arithmetic
- Sequence 2: Neither
- Sequence 3: Geometric
- Sequence 4: Arithmetic
- Sequence 5: Geometric