Question

ДАЮ 30 БАЛЛОВ
$P_{x+1} \leq 30P_{x-1}$

Answer 1

$P_{x+1}=(x+1)!\\\\P_{x-1}=(x-1)!\\\\(x+1)!\leq 30(x-1)!\\\\x!*(x+1)\leq 30*x!*(x-1)\ \ \mid\div x!\\\\(x+1)\leq 30(x-1)\\\\x+1\leq 30x-30\\\\-29x\leq -31\\\\x\geq \frac{31}{29} \\\\x\in[\frac{31}{29};+\infty)$