Đáp án:
1/1-2+-4+5-...+99-100
=(1-2)+(3-4)+.... +(99-100)
=(-1) + (-1)+...... + (-1)
=(-1) x 50
=-50
2/ 2-4+6-8+....+48-50
=(2-4)+(6-8)+....+(48-50)
= (-2)+(-2) + .... + (-2)
= (-2)x25
= -50
3/ -1+3-5+7 - 9+11-13+15-.... -96+97+98-99
=-1+3-5+7...+93-95+97-99
=-(1+3+5+7...+93+95+97+99)
=-2500
4/1+2-3-4+...+97+98-99
=1+(2-3-4+5)+....+(92-93-94+95)+(97+98-99)
=1+0+.....+0+99
=100
Bạn tham khảo .