Question

calcule a soma dos elementos da pa (-8,-1,6.....41)

Answer 1

(-8,-1,6.....41)
an=a1+(n-1)r
41=-8+(n-1)7
41=-8+7n-7
41+8+7=7n
56=7n
n=56/7
n=8

sn=(a1+an)n/2
s8=(-8+41)8/2
s8=33.4
s8=132