Question

[Kẻ giấu mặt]

a)E=1+3+6+...+5050

b)F=6+16+30+...+2040

c)G=2+5+9+...+10300;d)n!=1.2.3. ... .n-Rút gọn A=1.1!+2.2!+3.3!+....+n.n