Question

Consider the arithmetic series:1+9+17+25+ ...Write a formula for the sum of the 1st n terms in this series.

A)4n2 - 3n
B)6n2 - 7n
C)8n2 - 5n
D)10n2 - n

Answer 1

1st nth sum is given by:
n ---- Sum Expression
1 ---- 1 --- 4*1^2 -3*1
2 ---- 1+9 = 10 --- 4*2^2 -3*2
3 ---- 1+9+17 = 27 --- 4*3^2 -3*3
4 ---- 1+9+17+25 = 52 --- 4*4^2 -3*4

Therefore, the best expressions is;
Sum of 1st nth terms = 4n^2 - 3n

Then,
The correct answer is A.