C) 6 và 1/5.(-2/7)+14 và 4/5.(-2/7)
D) 7 và 1/6. (-7/6)+10 và 5/6.(-7/6)
E) 5/7.5/11+5/7.2/11-5/7.14/11
Ai làm nhanh mk vote 5star.
C) 6 và 1/5.(-2/7)+14 và 4/5.(-2/7) D) 7 và 1/6. (-7/6)+10 và 5/6.(-7/6) E) 5/7.5/11+5/7.2/11-5/7.14/11 Ai làm nhanh mk vote 5star.
By Valerie
`a) 6 1/5 .(-2)/7 + 14 4/5 .(-2/7)`
` = (-2)/7 .(6 1/5 + 14 4/5)`
` = (-2)/7 .[ (6+14) + (1/5 + 4/5)]`
` = (-2)/7 . (20 +1)`
` = (-2)/7 . 21`
`b) 7 1/6 .(-7)/6 + 10 5/6 .(-7)/6`
` = (-7)/6 .( 7 1/6 + 10 5/6)`
` = (-7)/6 . [(7+10) + (1/6+5/6)]`
` = (-7)/6 . (17 + 1)`
` = (-7)/6 . 18`
`c) 5/7 . 5/11 + 5/7 . 2/11- 5/7. 14/11`
` = 5/7. (5/11 + 2/11 – 14/11)`
` = 5/7 . (-7)/11`
`f) 19 5/8: 7/12- 15 1/4:7/12`
` = 19 5/8 . 12/7 – 15 1/4 . 12/7`
` = 12/7 .( 19 5/8 – 15 1/4)`
` = 12/7. [(19-15) + (5/8-1/4)]`
` = 12/7. (4 + 3/8)`
` = 12/7 . 4 3/8`
`g) 2/5. 1/3- 2/15 : 1/5+ 3/5. 1/3`
` = 2/5 . 1/3 – 2/15 . 5 + 3/5 . 1/3`
` = 2/5 . 1/3 – 2/3 + 3/5 . 1/3`
` =2/5 . 1/3 – 2.1/3 + 3/5 . 1/3`
` = 1/3.(2/5 – 2 +3/5)`
` =1/3. (-1)`
`h) 4/9. 19 1/3- 4/9. 39 1/3`
` = 4/9.(19 1/3 – 39 1/3)`
` = 4/9 . [(19 -39) + (1/3-1/3)]`
` = 4/9 . (-20)`
Giải thích các bước giải:
`a) 6 1/5 .(-2)/7 + 14 4/5 .(-2/7)`
` = (-2)/7 .(6 1/5 + 14 4/5)`
` = (-2)/7 .[ (6+14) + (1/5 + 4/5)]`
` = (-2)/7 . (20 +1) = (-2)/7 . 21`
$\\$
`b) 7 1/6 .(-7)/6 + 10 5/6 .(-7)/6`
` = (-7)/6 .( 7 1/6 + 10 5/6)`
` = (-7)/6 . [(7+10) + (1/6+5/6)]`
` = (-7)/6 . (17 + 1)= (-7)/6 . 18`
$\\$
`c) 5/7 . 5/11 + 5/7 . 2/11- 5/7. 14/11`
` = 5/7. (5/11 + 2/11 – 14/11) = 5/7 . (-7)/11`
$\\$
`f) 19 5/8: 7/12- 15 1/4:7/12`
` = 19 5/8 . 12/7 – 15 1/4 . 12/7`
` = ( 19 5/8 – 15 1/4).12/7 `
` = [(19-15) + (5/8-1/4)].12/7`
` = (4 + 3/8).12/7= 4 3/(8) . 12/7`
$\\$
`g) 2/5. 1/3- 2/15 : 1/5+ 3/5. 1/3`
` = 2/5 . 1/3 – 2/15 . 5 + 3/5 . 1/3`
` = 2/5 . 1/3 – 2/3 + 3/5 . 1/3`
` =2/5 . 1/3 – 2.1/3 + 3/5 . 1/3`
` = 1/3.(2/5 – 2 +3/5) =1/3. (-1)`
$\\$
`h) 4/9. 19 1/3- 4/9. 39 1/3`
` = 4/9.(19 1/3 – 39 1/3)`
` = 4/9 . [(19 -39) + (1/3-1/3)] = 4/9 . (-20)`