Предмет: Математика, автор: Djasurxon

решите пожалуйста....

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Автор ответа: HSS9860

1

Если воспользоваться свойствами арифметической и геометрической прогрессий:
1. a₁+a₃=2a₂
2. a₁*a₃=a₂²,
тогда можно а₁ найти из системы уравнений:
$\left \{ {{a_1+18=2a_2} \atop {a_1*24=a_2^2}} \right.$
Здесь получаются две пары чисел:
а₁=6; а₂=12 и
а₁=54; а₂=54, откуда только вторая пара удовлетворяет условию (убывающая прогрессия).
Ответ: а₁=54

HSS9860: // а_2=36, откуда только...

Аноним: вначале вы написали геометрическая прогрессия и написали арифматическую

HSS9860: Где именно?

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