The infinite sequence a1, a2, …, an, … is such that a1=2
The sum of the repeating sequence comes from simply figuring out how often the sequence repeats–in this case every 4 terms–and then adding this however many times the sequence itself fits into, in this case, 97.
So that’s four terms sum to 3, and we have 24 groups of 3 to make 96 terms. The final term is a_1 = 2.
The infinite sequence a1, a2,…, an, … is such that a_1=2, a_2=−3, a_3=5, a_4=−1, and a_n=a_(n−4) for n greater than 4. What is the sum of the first 97 terms of the sequence?
A. 72
B. 74
C. 75
D. 78
E. 80
GMAT #GRE #Quant #MIM #MBA
FREE Top Three 705+ Arithmetic Shortcuts (8-video course):
FREE Factoring Magic Video Course:
