Question

[TỰ TIN]

1+2+3+4+...+2000=?

2+4+6+...+1998=?

      XONG KB VỚI TUI NHA

Answer 1

[khai]

1+2+3+4+...+2000=(2000+1)×2000:2=2001000

2+4+6+...+1998=(1998+2)×999:2=999000

Answer 2

[emily]

1+2+3+4+...+2000= ( 2000+1)x [(2000-1) : 1 +1] :2 = 2001 x 2000 : 2 = 2001000

2+4+6+...+1998= ( 1998 +2) x [ ( 1998 - 2) : 2 +1] :2 = 2000 x 999 : 2 = 999000