Question

Which of the following is true about the sequence graphed below? (and Why)

Options:

• The sequence is arithmetic because the terms have a common difference.
• The sequence is arithmetic because the terms do not have a common difference.
• The sequence is not arithmetic because the terms have a common difference.
• The sequence is not arithmetic because the terms do not have a common difference.

Answer 1

Explanation:

The common difference is a y-thing. It looks like the difference in the y-values of each of these points is -1.5. That means that this is an arithmetic sequence because the common difference is consistently -1.5. In fact, the whole equation can be determined to be

`a_n=-1.5n+12`

Answer 2

Explanation:

a₂ = 9

a₃ = a₂-1.5

a₄ = a₃-1.5

a₅ = a₄-1.5

etc.

The terms have a common difference of -1.5, so the sequence is arithmetic.