Question

(5^n+1 - 5^n-1)/2*5^n

Answer 1

Решение:
$\frac{5 n^{n+1} - 5 n^{n-1} }{2* 5^{n} } = \frac{ 5x^{n-1}*( 5^{2} - 1) }{2* 5^{n}} = \frac{5x^{n-1}*24}{2* 5^{n}} = \frac{12}{5} = 2 \frac{2}{5}$
Ответ: 2,4.