a)=1+(2-3-4+5)+(6-7-8+9)+...+(994-995-996+997)+998
=1+0+0+...+0+998
=999
b)=(1-3)+(5-7)+...+(97-99)+101
=-2+(-2)+...+(-2)+101 (50 số hạng -2)
=-2.50+101
=-100+101
=1
a) = (2-3-4+5) + ..... + (993 - 994 - 995 + 996) + 997 + 998 + 1
= 998 + 997 + 1 = 1996
1+2-3-4+5+6-7-8+...........+993+994-996+997+998
=1+(2-3-4+5)+(6-7-8+9)+...........+(994-996+997+998)
=1+0+0+...........+?
=>Sai đề
b,1-3+5-7+..........+97-99+101
=(-2)+(-2)+..........+(-2)+101(50 số-2)
=(-2).50+101
=-100+101=1
a)
=(2-3-4+5)+.....+(993-994-995+996)+997+998+1
=998+997+1=1996