The first term of an arithmetic sequence is 30 and the common differenc eis -1.5.
a) Find the value of the 25th term.
The rth term of the sequence is 0.
b)Find the value of r.
The sum of the first n terms of the sequence is Sn.
c) Find the largest postitive value of Sn.
i worked out a and b but got stuck with c. Any help!
Hello, thereddemon!
Another approach . . .
Formula: .The first term of an arithmetic sequence is
. . and the common difference is
The sum of the first terms of the sequence is
c) Find the largest postitive value of
We have: .
. .
This is a down-opening parabola; its maximum is at its vertex.
. . The vertex is at: .
Therefore, maximim is: .