Question

calcular a soma dos 12 primeiros termos da p.a (-7,-4,-1,..)

Answer 1

a1=-7
a2=-4
razão=(-7)-(-4)=3
n=12


an=a1+(n-1).r
a12=7+(12-1).3
a12=7+11.3
a12=7+33
a12=40

sn=(a1+a12).n/2
s12=(-7+40).12/2
s12=33.6
s12=198