Câu 1: Thực hiện phép tính (tính hợp lí nếu có thể) a) 7/30 + -12/37 + 23/30 + -25/37 b) 1/2 + 13/19 - 4/9 + 6/19 + 5/18 c) -20/23 + 2/3 - 3/23 + 2/5 + 7/15 d) 4/3 + -11/31 + 3/10 - 20/31 - 2/5 e) 5/7 . 5/11 + 5/7 . 2/11 - 5/7 . 14/11 f) 2/11 . -5/4 + -9/11 . 5/4 + 1 3/4

Đáp án+Giải thích các bước giải:

a) `7/30 + -12/37 + 23/30 + -25/37`

 `= 7/30+23/30+ -12/37 + -25/37`

 `= 1 + -1`

 `= 0`

b) `1/2 + 13/19 - 4/9 + 6/19 + 5/18`

 `= 13/19 + 6/19 +1/2 - 4/9 + 5/18`

 `= 1 + 1/18 + 5/18`

 `= 1 + 6/18`

 `= 4/3`

c) `-20/23 + 2/3 - 3/23 + 2/5 + 7/15`

 `= -20/23 - 3/23 + 2/3 + 2/5 + 7/15`

 `= -1 +16/15 + 7/15`

 `= -1 + 23/15`

 `= 8/15`

d) `4/3 + -11/31 + 3/10 - 20/31 - 2/5`

 `= -11/31 - 20/31 + 4/3 - 2/5 + 3/10`

` = -1 + 37/30`

 `= 7/30`

e)` 5/7 . 5/11 + 5/7 . 2/11 - 5/7 . 14/11`

 `= 5/7. ( 5/11 + 2/11 - 14/11)`

 `= 5/7 . -7/11`

` = -5/11`

f) $2/11 . -5/4 + -9/11 . 5/4 + 1 \dfrac{3}{4}$

 `= 2/11 . -5/4 + -9/11 . 5/4 + 7/4`

 `= 5/4 . ( 2/11 + -9/11) + 7/4`

 `= 5/4 . -7/11 + 7/4`

 `= 21/22`