Answer:
20th term is 408
Step-by-step explanation:
Looking at the sequence we see the following pattern
n Term Diff
1 9 -
2 12 3
3 17 5
4 24 7
5 33 9
The difference between successive numbers is increasing by 2 for every successive n
The 6th term will be 33 + 9 + 2 = 44
We see that the nth term can be represented by
a(n) = a(1) + (n² - 1) with a(1), the first term being 9
a(n) = 9 + (n² - 1)
a(20) = 9 + (20² - 1)
a(20) = 9 + (400 - 1)
a(20) = 9 + 399
a(20) = 408
