(3n - 4)! = (3n-4)*(3n-5)! = 20(3n-5)! Отсюда (3n-4) = 20, а n=8.
ответ: n=8
(3n-4)!=20(3n-5)
3n-4=60n-100
3n-4-60n+100=0
3n-60n=-4+100
-57n=98
n=-1.68
(3n - 4)! = (3n-4)*(3n-5)! = 20(3n-5)!
Отсюда (3n-4) = 20, а n=8.
ответ: n=8
(3n-4)!=20(3n-5)
3n-4=60n-100
3n-4-60n+100=0
3n-60n=-4+100
-57n=98
n=-1.68