SOLUTION: the sum of the arithmetic serie whose first two terms are -12 and -8, respectively, and whose last term is 124.

Question 1180187: the sum of the arithmetic serie whose first two terms are -12 and -8, respectively, and whose last term is 124.
Found 2 solutions by mananth, MathLover1:
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
the sum of the arithmetic serie whose first two terms are -12 and -8, respectively, and whose last term is 124.
-12, -8, ...........124
a= -12, d=4, tn =124
tn = nth term = a+(n-1)d
124 = -12+(n-1)4
136 = 4n-4
140 = 4n
n= 35 There area 35 terms
Sum of terms Sn = (n/2) * (a+l) where a is the first term and l is the last term
Sn = (35/2) (-12+124)
= 35*112/2
35* 56 =1960
sum of the arithmetic series = 1960
Answer by MathLover1(20850) (Show Source): You can put this solution on YOUR website!

the sum of the arithmetic serie whose first two terms are and, respectively, and whose last term is

last term is
common difference is
nth term formula is:
....substitute given
......solve for

there are terms in this sequence, and they are
the sum is

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