Question

determine a soma dos 60 primeiros dos pa:
a)(1+5+9...)
b)(12+15+18+...)

Answer 1

Resposta:

an=a1+(n-1)*r

Sn=(a1+an)*n/2

razão=a2-a1

a)

a60=1+(60-1)*4=237

S60=(1+237)*60/2=7140

b)

a60=12+(60-1)*3 = 189

S60=(12+189)*60/2=6030