Question

quantos termos possui a pg (1/81,1/27,1/9...2187)

Answer 1

a1 = 1/81
a2 = 1/27
q = 1/27 : 1/81 = 1/27 * 81/1 = 81/27 = 3 ****
an = 2187
an = a1* q^n-1
2187 = 1/81 * 3^n-1
3^n-1 = 2187 : 1/81 = 2187 * 81  = 177147 = 3^11
3^n-1 = 3^11
n - 1 = 11
n = 12 *****