Explicație pas cu pas:
a)
6!×13-5!×12
13x6!-12x5!=
13x6x5!-12x5!=
78x5!-12x5!=
66x5!=66x120=7920
b)
6!-1!-2!-3!-4!=
6!-1-2-6-24=
720-9-24=
711-24=687
c)
7!-6!+5!-4!=
5040-720+120-24=
4320+120-24=
4440-24=4426
un număr factorial se afla:
ex:
7!=1x2x3x4x5x6x7
5!=1x2x3x4x5
4!=1x2x3x4