Question

calcule a soma dos termos da PA (3,6...669)

Answer 1

Boa tarde Cammu!

solução!

Vamos primeiro determinar a razão e em seguida encontra o termo geral da P.A.


$r=a2-a1\\\\\ r=6-3\\\\\ r=3$


$a1=6 \\\\\ n=? \\\\\ an=669 \\\\\ r=3$


Formula do termo geral.


$an=a1+(n-1).r$


$669=6+(n-1).3 \\\\ 669=6+3n-3 \\\\ 669=3+3n \\\\ 666=3n \\\\\ n= \dfrac{666}{3} \\\\\ n=222$


Formula da soma da P.A


$S= \dfrac{(a1+an).n}{2} \\\\\ S= \dfrac{(6+669).222}{2} \\\\\ S= (6+669).111 \\\\\ S=(672).111\\\\\ S=74592$


Boa tarde!
Bons estudos!