JAMB - Mathematics (1994 - No. 19)
Find the nth term of the sequence 3, 6, 10, 15, 21.....
\(\frac{n(n - 1)}{2}\)
\(\frac{n(n + 1)}{2}\)
\(\frac{(n + 1)(n + 2)}{2}\)
n(2n + 1)
Explication
\(\frac{(n + 1)(n + 2)}{2}\)
If n = 1, the expression becomes 3
n = 2, the expression becomes 6
n = 4, the expression becomes 15
n = 5, the expression becomes 21
If n = 1, the expression becomes 3
n = 2, the expression becomes 6
n = 4, the expression becomes 15
n = 5, the expression becomes 21