Question

[ta duc manh]

Tìm D=1x1!+2x2!+3x3!+4x4!+...+100x100! 

Answer 1

[Le Thi Khanh Huyen]

Ta có :

\(D=1.1!+2.2!+...+100.100!\)

\(=\left(2-1\right)1!+\left(3-1\right).2!+\left(4-1\right).3!+...+\left(101-1\right).100!\)

\(=2!-1!+3!-2!+4!-3!+...+101!-100!\)

\(=101!-1!\)

Số quá lớn nhé :)