Câu hỏi 14Tính $\dfrac3{1!+2!+3!}+\dfrac4{2!+3!+4!}+\cdots+\dfrac{22}{20!+21!+22!}$.$\frac1{2!}-\frac1{22!}$$\frac1{3!}-\frac1{22!}$$\frac1{2!}-\frac1{21!}$$\frac1{3!}-\frac1{21!}$$\frac1{4!}-\frac1{22!}$