Posted by albert on .
A sequence is defined by
un = 2×(−0.5)n + 3 (n = 1,2,3, . . .).
Choose the option that best describes the long-term behaviour of the
A un becomes arbitrarily small (that is, un → 0 as n→∞).
B un becomes arbitrarily large and negative (that is, un →−∞
C un approaches 3 as n→∞ (that is, un → 3 as n→∞).
D un is unbounded and alternates in sign.
E un becomes arbitrarily large and positive (that is, un→∞
F un approaches 2 as n→∞ (that is, un → 2 as n→∞
Look at the behaviour of the first term:
2*(-0.5)^n (check, this is not what you posted).
We can make the following observations.
As n increases, the sign alternates.
As n->∞ the term approaches zero.
Based on these observations, can you make a choice from the list of possible answers? In the worst case, you should be able to eliminate quite a few choices.