Tính
A = 1 - 2 + 3 - 4 + 5 - 6 + 7 - 8 + 9 - ........... + 2019
B = 1 + 2 - 3 + 4 - 5 + 6 - 7 + .............. + 2017 + 2018 - 2019 + 2020
a) 5+3.(-7)+4:(-2)
b)1-2-3+4+5-6-7+8.....+2017-2018-2019+2020+2021
B= 1+2-3-4+5+6-7-8+9+10-...+2018-2019-2020+2021
1 - 2 + 3 - 4 + 5 - 6 + 7 - 8 + ..... + 2019 - 2020 + 2021
1-2+3-4+5-6+7-8+...+2019-2020+2021
1-2+3-4+5-6+7-8+...+2019-2020
1+2-3-4+5-6-7-8+...-2019-2020+2021+2022
Tính hợp lí:
a. A= -1 + 3 - 5 + 7 - 9 +....- 2017 + 2019
b. B= 2 - 4 + 6 - 8 +...+ 2018 - 2020
c. C= 1 + 2 - 3 - 4 + 5 + 6 - 7 - 8+...-111 - 112 + 113 + 114 + 115
1+2-3-4+5+6-7-8-....-2019-2020+2021+2022 help