Question

o vigesimo termo da p.a.(5;8;...)

Answer 1

$a_{n} = a_{1} +(n-1)r \\ \\ a_{n} = a_{(n-1)} +r \\ \\ a_{1} =5 \\ \\ a_{2} =8 \\ \\ a_{2} = a_{1} +r \\ \\ 8=5+r \\ \\ r=8-5=3 \\ \\ \\ a_{20} = a_{1} +(20-1).3 \\ \\ a_{20} =5+19.3=62$