b1 = n; b2 = n+15; b3 = 46n - 30
По характ св-ву геометрической прогрессии
b2 ( в квадрате) ^2 = b1 × b3
(n+15)^2 = n × (46n -30)
n^2 + 30 n +225 = 46n^2 - 30n
-45n^2 +60n +225 = 0
3n^2 - 4n -15 = 0
D = 16 - 4 × 3 × (-15)
D = 196
√D = 14
n1 = (4 + 14 ) 2 × 3 = 3
n2 = (4-14)2×3 = -5/3
b1 = 3 или -5/3
b2 18 или 40/3.
b3 108 или -320/3
Вроде так)
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b1 = n; b2 = n+15; b3 = 46n - 30
По характ св-ву геометрической прогрессии
b2 ( в квадрате) ^2 = b1 × b3
(n+15)^2 = n × (46n -30)
n^2 + 30 n +225 = 46n^2 - 30n
-45n^2 +60n +225 = 0
3n^2 - 4n -15 = 0
D = 16 - 4 × 3 × (-15)
D = 196
√D = 14
n1 = (4 + 14 ) 2 × 3 = 3
n2 = (4-14)2×3 = -5/3
b1 = 3 или -5/3
b2 18 или 40/3.
b3 108 или -320/3
Вроде так)