Question

Решите уравнение A^2x+1=20

Answer 1

Aₐᵇ = a!/(a - b)!

Aₓ₊₁² = 20

(x+1)!/(x - 1)! = 20

x>1

x(x + 1) = 20

x² + x - 20 = 0

D = 1 + 80 = 81

x12 = (-1 +- 9)/2 = -5  

x = -5 < 1 нет

x = 4 > 1 да

ответ 4

A₅² = 5!/3! = 4*5 = 20