Answer:
No
Step-by-step explanation:
To find out, all we need to do is plug in 9999 into the sequence.
[tex]9999 = n^2 + 2n[/tex]
By completing the square, we get [tex](n+1)^2 = 1001[/tex]. 1001 is not a perfect square, which means that 9999 is not in the sequence.
hope this helped! :)
