Question

Sabe-se que em uma PA de 12 termos
a1= -8 a12= 36 . Calcule a razão dessa PA

Answer 1

$\boxed{a_n=a_1+(n-1)*r}\\\\ a_1_2=a_1+11r\\\\ 36=-8+11r\\\\ 11r=36+8\\\\\ 11r=44\\\\ r=\frac{44}{11}\\\\ \boxed{\boxed{r=4}}$