SOLUTION: Suppose that the eighth term of an arithmetic sequence is 59, and also suppose that the twenty first term of the same arithmetic sequence is 150. Find an explicit formula for the

Algebra ->  Sequences-and-series -> SOLUTION: Suppose that the eighth term of an arithmetic sequence is 59, and also suppose that the twenty first term of the same arithmetic sequence is 150. Find an explicit formula for the       Log On


   



Question 870500: Suppose that the eighth term of an arithmetic sequence is 59, and also suppose that the twenty first
term of the same arithmetic sequence is 150. Find an explicit formula for the general term of this
arithmetic sequence.

Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
t8 = 59 = a+7d..............(1)
t21= 150 =a+20d.............(2)
solve (1) & (2)
subtract (2) from (1)
-13d =-91
d=7
a+7d=59
substitute d
a+49=59
a=10
tn = a+(n-1)d
tn = 10+(n-1)7
=10+7n-7
=7n+3