Question

Qual o vigésimo termo da progressão aritmética (-8,-3,2,7,...) ?

Answer 1

an= a1 + ( n-1 ) . r
a20= -8 + ( 20-1 ). 5
a20= -8+19.5
a20= -8+95
a20= 87

Answer 2

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