Question

dada a sequencia numerica (5,9,13,21,25,29,29,33,37) determine o 20° termo dessa PA an=a1+(n-1).r

Answer 1

$a_{2} = a_{1} +r \\ \\ 9=5+r \\ \\ r=9-5=4 \\ \\ \\ a_{1} =5 \\ \\ r=4 \\ \\ a_{20} =5+(20-1).4 \\ \\ a_{20} =5+19.4=81$