Question

What is the sum of a 17-term arithmetic sequence where the first term is 6 and the last term is -90?

Answer 1

i got a huge # like -12138

Answer 2

but its not right

Answer 3

the sum is -714.
the sum is given by the formula
S= n/2[a+l], where n is the no. of terms, a is the first term and l is the last term.

Answer 4

I get that and i used that formula but i didnt do it right i guess.....