Respostas

2014-08-15T20:08:32-03:00
A1=9
r= 7
a6=a1+(n-1)r
a6=9+(6-1)7
a6=9+5*7
a6=9+35=44

sn=(a1+an)n/2
s6=(a1+a6)n/2
s6=(9+44)6/2
s6=53*3
s6=159