Question

determine a razao e 1 termo em que a6+a15=-41 e a3+a17=-38

Answer 1

A razão:

$a_{6}+a_{15}=-41\\a_3+a_{17}=-38\\----------------\\a_1+5r+a_1+14r=-41\\a_1+2r+a_1+16r=-38\ \ *(-1)\\----------------\\a_1+5r+a_1+14r=-41\\-a_1-2r-a_1-16r=38 \ \ \ \ Soma-se \ os \ dois \ valores\\----------------\\3r-2r=-3 \\\boxed{\boxed{r=-3}}$


O primeiro termo:

$a_1+5r+a_1+14r=-41 \\ 2a_1+19r=-41\\2a_1+19*(-3)=-41\\2a_1-57=-41\\2a_1=-41+57\\2a_1=16\\a_1= \frac{16}{2} \\ \boxed{\boxed{a_1=8}}$