Bài 1
A = -5/7 + 3/4 + (-1/5) + (-2/7) + 1/4
= [(-5/7) + (-2/7)] + (3/4 + 1/4) + (-1/5)
= (-1) + 1 + (-1/5)
= -1/5
B = -3/17 + (2/3 + 3/17)
= -3/17 + 3/17 + 2/3
= 2/3
C = 1/2 - 43/101 + (-1/3) - 1/6
= (1/2 - 1/3 - 1/6) - 43/101
= 0 - 43/101
= -43/101
D = (-13/7 - 4/9) - (-6/7 - 4/9
= (-13/7 + 6/7) + (-4/9 + 4/9)
= -1 + 0
= -1