Question

determine o 9° termo da PG(81,27,9,...)

Answer 1

an=a1*q^n-1 
a9=a1*q^8 
a1=81 
q=27/81=1/3 
a9=81*(1/3)^8 
a9=81*1/59049 
a9=81/59049 
a9=1/729

Answer 2

a9 = a1 . q^n-1
a9 = 81 . (1/3)^9-1
a9 = 81 . (1/3)^8
a9 = 3^4 . 3^-8
a9 = 3^-4
a9 = (1/3)^4
a9 = 1/81