Task 1
The sum Sn of a finite arithmetic series of n terms is Sn
the nth term.
(a1 + an) where ai is the first term and an is
2
nin1
a. Show that Sn = nai + d by replacing an with its value in terms of ai, n, and d in the above
formula
b. Explain why Sn = nai +
n (11-1)
d makes sense by explaining how you can extract each of na and
(n-1)
2 -d from the sum a1 + (a1 + d) + (a1 + 2d) + ... + (a1 + (n − 1)d).
2