Question

решите уравнение срочно

Answer 1

$\displaystyle A_n^m=\frac{n!}{(n-m)!}; C_n^m=\frac{n!}{m!(n-m)!}\\\\\frac{x!}{(x-2)!}-\frac{x!}{(x-1)!(x-x+1)!)}=24\\\\\frac{x!}{(x-2)!}-\frac{x!}{(x-1)!}=24\\\\\frac{x!}{(x-2)!}*(1-\frac{1}{x-1})=24\\\\x(x-1)*\frac{x-1-1}{x-1}=24\\\\x(x-2)=24\\\\x^2-2x-24=0\\\\D=4+96=100\\\\x_{1.2}=\frac{2 \pm 10}{2}\\\\x_1=6; x_2=-4 (ne-podxodit)$

Ответ х=6