Пошаговое объяснение:
Дано: b2 = 1/2; b4 = 1/4
Знайти: S7
b2 = b1 * q
b4 = b1 * q³
q² = 1/4 : 1/2 = 1/4 * 2 = 1/2
q = ±1/√2
b1 = 1/2 : 1/√2 = √2/2
S7 = b1 * (q^6 - 1/(1 - q) = √2/2 * (/1/√2)^6 - 1)/(1 - 1/√2) =
=√2/2 * (1/8 - 1)/(√2 - 1)/√2 = -7/(8 * (√2 - 1) = -7(√2-1)/8
Пошаговое объяснение:
Дано: b2 = 1/2; b4 = 1/4
Знайти: S7
b2 = b1 * q
b4 = b1 * q³
q² = 1/4 : 1/2 = 1/4 * 2 = 1/2
q = ±1/√2
b1 = 1/2 : 1/√2 = √2/2
S7 = b1 * (q^6 - 1/(1 - q) = √2/2 * (/1/√2)^6 - 1)/(1 - 1/√2) =
=√2/2 * (1/8 - 1)/(√2 - 1)/√2 = -7/(8 * (√2 - 1) = -7(√2-1)/8