Найдите восьмой член прогрессии bn если b1 равно 162 и b3 равно 18

B3 = b1*q^2 ==>

162*q^2 = 18
q^2 = 1/9
q = ± 1/3

1) q = 1/3
b8 = b1*q^7 = 162*(1/3)^7 = 162/2187 = 2/27
2) q = - 1/3
b8  = b1*q^7 = 162*(-1/3)^7 = - 162/2187 = - 2/27

ответ
± 2/27

В1=162; в3=18;
q^2=b1÷b2=18÷162=1/9;
q=-1/3; q=+1/3;

1)q=-1/3; b8=b1q^7=162 × (-1/3)^7=
=-162×1/2187=-2/27;

q=1/3; b8=162 × (1/3)^7=162 × 1/2187=2/27.