Đáp án + Giải thích các bước giải:
Bài `1`:
a, `-7/15 - 3/25`
` = -35/75 - 9/75`
` = -44/75`
b, `-4/5 : (-8/15)`
` = -4/5 . (-15)/8`
` = 3/2`
c, `3/5 . 7/9 + 3/5 . 2/9 + 3/5`
` = 3/5 . (7/9 + 2/9) + 3/5`
` = 3/5 . 1 + 3/5`
` = 3/5 + 3/5 = 6/5`
d, `-1/12 - (2 5/8 - 1/3)`
` = -1/12 - (21/8 - 1/3)`
` = -1/12 - 21/8 + 1/3`
` = (4/12 - 1/12) - 21/8`
` = 1/4 - 21/8`
` = 2/8 - 21/8`
` = -19/8`
e, `-1/24 - [1/4 - (1/2 - 7/8)]`
` = -1/24 - (1/4 - 1/2 + 7/8)`
` = -1/24 - 1/4 + 1/2 - 7/8`
` = -1/24 - 6/24 + 12/24 - 21/24`
` = -16/24 = -2/3`
f, `( (0,4 - 2/9 + 2/11)/(1,4 - 7/9 + 7/11) - (1/3 - 0,25 + 1/5)/(1 1/6 - 0,875 + 0,7) ) : 2012/2013`
` = ( (2/5 - 2/9 + 2/11)/(7/5 - 7/9 + 7/11) - (2/6 - 2/8 + 2/10)/(7/6 - 7/8 + 7/10) ) : 2012/2013`
` = ( ( 2 . (1/5 - 1/9 + 1/11) )/( 7 . (1/5 - 1/9 + 1/11) ) - (2 . (1/6 - 1/8 + 1/10) )/( 7 . (1/6 - 1/8 + 1/10) ) ) : 2012/2013`
` = (2/7 - 2/7) : 2012/2013`
` = 0 : 2012/2013 = 0`