Question

срочно нужна помощь другу

Answer 1

$frac{x}{A_x^3} = frac{1}{12} , \ frac{x}{frac{x!}{(x-3)!}} = frac{1}{12} , \ frac{x}{(x-2)(x-1)x} = frac{1}{12} , \ frac{1}{(x-2)(x-1)} - frac{1}{12} = 0, \ frac{12-(x-2)(x-1)}{12(x-2)(x-1)} = 0, \ -12+x^2-3x+2=0, \ x^2-3x-10=0, \ x_1=-2 textless 0, x_2=5, \ x=5.$