Verified answer

Ответ:

2.4

Пошаговое объяснение:

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Verified answer

a^m*a^n = a^(m + n)

(5^(n + 1) - 5^(n - 1)) / 2*5^n = (5^(n - 1)*(5^2 - 1) / 2*5*5^(n - 1) = (25 - 1)/10 = 24/10 = 12/5 = 2.4