Question

calcular x ! .(x + 1 )!=20 (x - 1 )! . x !​

Answer 1

x ! .(x + 1 )!=20 (x - 1 )! . x ! ==> :(x!)

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

(x+1).x.(x-1)! = 20(x-1)! ==> :(x-1)!

x²+x - 20 = 0

∆= 1+80= 81 => √∆=9

x' = -1+9/2 = 4