Question

Записать формулу n-го члена геометрической прогрессии :
1) 4, 12 , 36 ...
2) 4 , -1 , 1/4 ...

Answer 1

1) 
4, 12, 36
b1 = 4
b2 = 12
q = b2/b1 = 12/4 = 3

bn = b1*q^(n - 1) = 4*3^(n - 1) = 4/3*4^n

2)
4, - 1, 1/4
b1 = 4
b2 = - 1
q = b2/b1 = - 1/4

bn = 4*(-1/4)^(n - 1) = - 16*(-1/4)^n