Question

please help ASAP for the brainliest answer

Answer 1

Answer:

arithmetic sequence

Step-by-step explanation:

The next number is 21

Answer 2

Answer:

Triangular Number Sequence

21

Step-by-step explanation:

This sequence is called the Triangular Number Sequence.

To find the next term, add 6 to 15.

The next term in the sequence is 21.