Question

Biết: n! =1.2.3...n. Tính: 1.1! + 2.2! + 3.3! + 4.4! + 5.5! =

Answer 1

1.1!+2.2!+3.3!+4.4!+5.5!=1.1+2.2+3.6+4.24+5.120

=1+4+18+96+600

=719

Answer 2

^{sai rồi} 

^{vừa làm xong}