Tìm x : -8 < x < 0

1.tim x
a, -8 < x < 0
b, -100 < x < 99
c, -10 < x < 5
2.tinh
a, A = 1 - 2 + 3 - 4 +...+ 2023 - 2014
b, B = - 2 + 4 - 6 + 8 +...- 2022 + 2024