find the common difference of the arithmetic sequence -1, 8, 17, ...

Explanation:

Step1: Recall common - difference formula

The common difference $d$ of an arithmetic sequence is given by $d=a_{n + 1}-a_{n}$, where $a_{n+1}$ and $a_{n}$ are consecutive terms.

Step2: Select two consecutive terms

Let $a_{1}=-1$ and $a_{2}=8$.

Step3: Calculate the common difference

$d=a_{2}-a_{1}=8-(-1)=8 + 1=9$.

Answer:

$9$