What is the n-th term of the sequence 2, 6, 12, 20…?
-
A.
4n – 2 -
B.
2(3n – 1) -
C.
n2 + n -
D.
n2 + 3n + 2
Correct Answer: Option C
Explanation
Given that 2, 6, 12, 20…? the nth term = n2 + n
check: n = 1, u1 = 2
n = 2, u2 = 4 + 2 = 6
n = 3, u3 = 9 + 3 = 12
∴ n = 4, u4 = 16 + 4 = 20