Question

a resposta dos trinta primeiros termos da pa ( - 15, - 11, - 7, - 3, ...)

Answer 1

$a_{30}=a_1+29.r\\ \\ a_{30}=-15+29.4=101\\ \\ S_{30}=\frac{30(a_1+a_{30})}{2}=\frac{30(-15+101)}{2}=1290$