(n - k)/(k + 1) * (n über k) = (n über k + 1)
(n - k)/(k + 1) * n!/(k! * (n - k)!) = n!/((k + 1)! * (n - k - 1)!)
(n - k)/(k + 1) * n!/(k! * (n - k) * (n - k - 1)!) = n!/((k + 1)! * (n - k - 1)!)
1/(k + 1) * n!/(k! * (n - k - 1)!) = n!/((k + 1)! * (n - k - 1)!)
n!/(k! * (k + 1) * (n - k - 1)!) = n!/((k + 1)! * (n - k - 1)!)
n!/((k + 1)! * (n - k - 1)!) = n!/((k + 1)! * (n - k - 1)!)
wzbw.