Question

Qual o 20° termo da P.A (-8,-3,2,7,...)

Answer 1

.
$a_n=a_{20}~~~~~~a_1=-8~~~~ n=20~~~~~r=-3-(-8)=-3+8=5 \\ \\ a_n=a_1+(n-1)r \\ \\ a_{20}=-8+(20-1).5 \\ \\ a_{20}=-8+(19)5 \\ \\ a_{20}=-8+95 \\ \\ a_{20}=87$

Answer 2

$\begin{array}{l}\sf a_n=a_1+(n-1)\cdot r\\\\\sf a_{20}=-8+(20-1)\cdot5\\\\\sf a_{20}=-8+19\cdot5\\\\\sf a_{20}=-8+95\\\\\boxed{\boxed{\sf a_{20}= 87}} \end{array}$