Question

Помогите решить уравнение комбинаторики.

Answer 1

$A_{x}^{4} :C_{x-1}^{3}=60\\\\\frac{x!}{(x-4)!} :\frac{(x-1)!}{3!*(x-1-3)!}=60\\\\\frac{x!}{(x-4)!}*\frac{3!*(x-4)!}{(x-1)!}=60\\\\\frac{(x-4)!*(x-3)(x-2)(x-1)x}{(x-4)!}*\frac{1*2*3*(x-4)!}{(x-4)!(x-3)(x-2)(x-1)}=60\\\\6x=60\\\\x=10$

Answer 2

............................