Bài 1:
a) (-2/3 + 3/7) : 4/5 + (-1/3 + 4/7) : 4/5
=[(-2/3 + 3/7) + (-1/3 + 4/7)] : 4/5
=[-2/3 + 3/7 + -1/3 + 4/7] : 4/5
=[(-2/3 + -1/3)+(3/7 + 4/7) : 4/5
= [ (-1) + 1 ] : 4/5
= 0 : 4/5
= 0
b) 5/9 : (1/11 - 5/22) + 5/9 : (1/15 - 2/3)
= 5/9 : (2/22 - 5/22) + 5/9 : (1/15 - 10/15)
=5/9 : (-3/22) + 5/9 : (-3/5)
=5/9 : [(-3/22)+(-3/5)
=5/9 : -81/110
= -550/729
Bài 2:
a)(2008 - 2/135 + 1/50) - (1 - 7/135 + 4/50) - (5 + 5/135 - 3/50)
= 2008 - 2/135 + 1/50 - 1 + 7/135 - 4/50 - 5 - 5/135 + 3/50
=(2008 - 1 - 5)+(-2/135 + 7/135 - 5/135)+(1/50 - 4/50 + 3/50)
= 2002 +( 5/135 - 5/135 ) + ( -3/50 + 3/50)
= 2002 + 0 + 0
= 2002
b)50 - 4/13 + 2/15 - 2/17
_____________________________
100 - 8/13 + 4/15 - 4/17
= 50 - 4/13 + 2/15 - 2/17
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2.50 + 2. 4/13 + 2 . 4/15 - 2 . 2/17
= 50 - 4/13 + 2/15 - 2/17
______________________________
2.(50 - 4/13 + 2/15 - 2/17)
= 1/2
