Question

Determine a soma dos termos da PA (6, 10, 14, ..., 134 ).

Answer 1

An= a1+(n-1)r
134= 6+(n-1)4     r=10-6=4
134=6+ 4n-4
134-6+4=4n
4n=132
n=132:4
n= 33

S33= [9a1+an).n]:2
S33= [6+134).33):2
s33=( 140,33) ;2
S33= 4620:2
S33=2310