Joanne,

The letter n indicates which term you are looking at

when n = 1 you have the first term,
when n = 2 you have the second term,
when n = 3 you have the third term,
and so on.

So to find the first term let n = 1 and you get

n² + 3n = 1² + 3 × 1 = 1 + 3 = 4.

To find the second term let n = 2 and you get

n² + 3n = 2² + 3 × 2 .

To find the second term let n = 3, and so on.

You need to read carefully because sometime the sequence starts with n = 0 rather than n = 1. So if your sequence is n² + 3n for n = 0, 1, 2, ... the first term would be

n² + 3n = 0² + 3 × 0 = 0 + 0 = 0,

and the second term would be

n² + 3n = 1² + 3 × 1 = 1 + 3 = 4.

I hope this helps,
Penny