Решите пожалуйста номер 18(2,4)
2) q = 1/3 b5 = 1/81
b5 = b1*q^4
b1 = b5/q^4 = (1/81) * 81 = 1
Sбеск убывающей геом прогрессии = b1/1-q = 1/(1 - 1/3) = 1/(2/3) = 1.5
4) q = -1/2
b4 = 1/8
b4 = b1*q^3
b1 = b4/q^3 = 1/8 * (-8) = -1
S = b1/1-q = -1 / (1 + 1/2) = -1/(3/2) = -2/3