Đáp án: 1=-10
Giải thích các bước giải:
a, 1 + -2 + 3 + -4.. 19+-20
=(1+19)+(-2+-18)...+(-10)+...+(-20)
=20+(-20)+20+(-20)+20...+10+(-20)
=-10
b, 1- 2 + 3 - 4 + ...99 - 100
=(1+99)-(2+98)...-(55+45)
=-50
Các phần còn lại tương tự
Đáp án:
1/1+(-2)+3+(-4)+....+19+(-20)
=-1+(-1)+....+(-1)
=-1.10
2/1-2+3-4+...+99-100
=-1.50
3/2-4+6-8+...+48-50
=-2+(-2)+...+(-2)+(-2)
=-2.12
=-24
4/-1+3-5+7-...+97-99
=-(1+3+5+7+....+97+99)
=-2500
5/1+2-3-4+5-...+97+98-99-100
=1+(2-3-4+5)+...+(94-95-96+97)+(98
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