Question

Calcule a soma dos termos da p.a (-8,0,8,....,112)

Answer 1

An=a1+(n-1).r
112=-8+(n-1).8
112+8=8n-8
120=8n-8
120+8=8n
128=8n
128/8=n
n=16
Sn=(a1+an).n/2
S16=(-8+112).16/2
S16=104.16/2
S16=1664/2
S16=832