Question

Выберите ответ:
1
1/15
2/15
3/7

Answer 1

Aₐᵇ = a! / (a - b)!

Cₐᵇ = a! /b! (a - b)!

C₇³ = 7! / 3!(7 - 3)! = 7! / 3!*4!

C₇⁵ = 7! / 5!*(7 - 5)! = 7! / 5!*2!

A₁₀⁷ = 10! / (10 - 7)! = 10! / 3!

1 / A₁₀⁷ = 3! / 10!

C₇³ + C₇⁵ = 7! / 3!*4!  + 7! / 5!*2!  = 7!*(5/3!*5! + 3/3!*5! ) = 8!/3!*5!

6! (C₇³ + C₇⁵ ) /  A₁₀⁷ = 6! 8! /3!5! * 3!/10! = 6!/5! * 8!/10! = 6 / 9*10 = 1/15