Question

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

Answer 1

$\boxed{a_n=a_1+(n-1)*r}\\\\\ a_1_2=a_1+11r\\\\ a_1_2=1+33\\\\ \boxed{a_1_2=34}$

$\boxed{S_n=\frac{(a_1+a_n)*n}{2}}\\\\ S_1_2=\frac{(1+34)*12}{2}\\\\ S_1_2=35*6\\\\ \boxed{S_1_2=210}$