`a, 3/7 + (-3/8) + 4/7 + (-5/8)` ( Câu này mình sửa lại đề cho dễ làm nhé )
= `( 3/7 + 4/7 ) + ( -3/8 - 5/8 )`
= `1 + (-1)`
= `0`
`b, 1/2 + 2/3 + 3/4 + (-4/5) + 5/6 + (-6/7) + 7/8 + 6/7 + (-5/6) + 4/5 + (-3/4) + (-2/3) + (-1/2)`
= `( 1/2 - 1/2 ) + ( 2/3 - 2/3 ) + ( 3/4 - 3/4 ) + ( -4/5 + 4/5 ) + ( 5/6 - 5/6 ) + ( -6/7 + 6/7 ) + 7/8`
= `7/8`
`c, 1/2 + (-3/4) + 3/5 + 1/57 + (-1/36) + 1/15 + (-2/9)`
= `( 1/2 - 3/4 - 1/36 - 2/9 ) + ( 3/5 + 1/15 ) + 1/57`
= `( 18/36 - 27/36 - 1/36 - 8/36 ) + ( 9/15 + 1/15 ) + 1/57`
= `-1/2 + 2/3 + 1/57`
= `1/6 + 1/57`
= `7/38`
`d, 1/2 + (-1/5) + (-5/7) + 1/6 + (-3/35) + 1/3 + 1/41`
= `( 1/2 + 1/6 + 1/3 ) + ( -1/5 - 5/7 - 3/35 ) + 1/41`
= `( 3/6 + 1/6 + 2/6 ) + ( -7/35 - 25/35 - 3/35 ) + 1/41`
= `1 + (-1) + 1/41`
= `1/41`
