Question

tinh nhanh 1 + -2 + 3 + -4 + 5 + -6 +...+ 2005 + -2006 + 2007

Answer 1

1+ -2+3+ -4+5+ -6+...+2005+ -2006+2007

=(1+ -2)+(3+ -4)+(5+ -6)+...+(2005+ -2006)+2007

=-1+-1+-1+...+-1+2007

=-1.1003+2007

=-1003+2007

=1004

Answer 2

= (-1) + (-1) +(-1)+ ...+(-1)

=-1^1003

=1 . -1 = 0

k  mình nha !