Question

calcule a soma dos 40 primeiros termos da PA (4,9,...)

Answer 1

40=4+39r
40=199

sn= (4+199)40/2
sn=160+7960/2
sn=8120/2
sn=4060 Soma dos termos 

an=4+(40-1)5
an=4+200-5
an=4+195
an= 199  o ultimo termo da pa