Question

qual 1° termo da p.g em que a4=81 e q=3

Answer 1

$\boxed{a_n=a_1*q^n^-^1}\\\\\ a_4=a_1*q^3\\\\ 81 = a_1*3^3\\\\ 81 = a_1*27\\\\\ a_1=\frac{81}{27}\\\\ \boxed{\boxed{a_1=3}}$