Problema Solution
If the first term of a sequence is 3 and the 4th Term of a sequence is 15, write an explicit rule and determine the 40th sequence.
Answer provided by our tutors
There is an information missing about what kind of sequence is in the question, arithmetic or geometric sequence?
Assuming the sequence is arithmetic we can write:
a1 = 3
a2 = 3 + d
a3 = 3 + 2d
a4 = 3 + 3d
3 + 3d = 15
d = 4
an = 3 + (n - 1)d
an = 3 + (n - 1)*4
an = 4n - 1 is the explicit rule
a40 = 4*40 - 1
a40 = 159 is the 40th sequence