Question

What is the sum of a 17-term arithmetic sequence where the first term is 7 and the last term is -105?

Answer 1

Sum of AS= (first term +last term) x (no of terms) /2
= [7+ (-105)] x 17 /2
Can you solve it?

Answer 2

-833..

Answer 3

I got the same answer as you.

Answer 4

THIS VERY COMPLETE . . .
\[n=17,a=7,U _{n}=-105\]
So
\[S _{n}=(n/2)(a+U _{b})=(17/2)(7-105)=17*(-98)=-833\]

Answer 5

I mean
\[S _{n}=(n/2)(a+U _{n})\]