Answer:
Arithmetic sequence.
Explanation:
We have been given 9,5,1 and -3
We need to check what kind of sequence is this.
![d=a_2-a_1](https://img.qammunity.org/2020/formulas/mathematics/middle-school/23fvfcvh4hgrr1vbqh1zust89xwntltkcl.png)
d is common difference we will check difference of consecutive terms.
![5-9=-4](https://img.qammunity.org/2020/formulas/mathematics/middle-school/g4rm6oqusbt326qj0ixot6scqxqt6msane.png)
![1-5=-4](https://img.qammunity.org/2020/formulas/mathematics/middle-school/xrnb6ouvphoertlnki1eg0ngzgod56e8dg.png)
![-3-1=-4](https://img.qammunity.org/2020/formulas/mathematics/middle-school/yg6a1srabltuqi3cbvv65gqmyut3ig66i0.png)
We can see the difference between all the terms are same that is -4
So, this is an arithmetic sequence.
Arithmetic sequence is the sequence in which the difference between consecutive terms are same.