Đáp án+Giải thích các bước giải:
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`2.`
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`A= (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)`
`A= (2/5-2/9+2/11)/(7/5-7/9+7/11)-(1/3-1/4+1/5)/(7/6-7/8+7/10)`
`A= (2.(1/5-1/9+1/11))/(7.(1/5-1/9+1/11))-(1/3-1/4+1/5)/(7/2(1/3-1/4+1/5))`
`A= 2/5-1/(7/2)`
`A= 2/5-1. 2/7`
`A= 2/5-2/7`
`A= 4/35`
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`B= (0,125-1/5-1/7)/(0,375-3/5+3/7)+(1/2+1/3-0,2)/(3/4+0,5-3/10)`
`B= (1/8-1/5-1/7)/(3/8-3/5+3/7)+(1/2+1/3-1/5)/(3/4+1/2-3/10)`
`B= (1/8-1/5-1/7)/(3.(3/8-3/5+3/7))+(19/30)/(19/20)`
`B= 1/3+19/30 . 20/19`
`B= 1/3 + 2/3`
`B= 1`
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`C= (1/9-1/7-1/11)/(4/9-4/7-4/11)+(3/5-3/25-3/125-3/625)/(4/5-4/25-4/125-4/625)`
`C= (1/9-1/7-1/11)/(4.(4/9-4/7-4/11))+(3.(1/5-1/25-1/125-1/625))/(4.(1/5-1/25-1/125-1/625))`
`C= 1/4+ 3/4`
`C= 1`
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`D= ((1+2+3+...+100)(1/3-1/5-1/7-1/9)(6,3.12-21.3,6))/(1/2+1/3+1/4+...+1/100)`
`D= ((1+2+3+...+100)(1/3-1/5-1/7-1/9)(75,6-75,6))/(1/2+1/3+1/4+...+1/100)`
`D= ((1+2+3+...+100)(1/3-1/5-1/7-1/9).0)/(1/2+1/3+1/4+...+1/100)`
`D= 0/(1/2+1/3+1/4+...+1/100)`
`D= 0`
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`3.`
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`A= ((1+17) + (1+17/2) + (1+17/3) +... + (1+17/19))/((1+19 + (1+19/2) + (1+19/3) +... + (1+19/17)`
`A= (18. 19/2. 20/3...36/19)/(20. 21/2. 22/3...36/17`
`A= ((18.19.20...36)/(2.3...19))/((20.21.22...36)/(2.3.17))`
`A= (18.19.20...36)/(2.3...19) . (2.3...17)/ (20.21.22...36)`
`A= (18.19.20...36.2.3...17)/(2.3...19.20.21.22...36)`
`A= 1`
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`B= (1/10-1)(1/11-1)(1/12-1)...(1/99-1)(1/100-1)`
`B= (-9/10)(-10/11)(-11/12)...(-98/99)(-99/100)`
`B= ((-9).(-10).(-11)...(-98).(-99))/(10.11.12...99.100)`
`B= ((-9).[(-10).(-11)...(-98).(-99)])/((10.11.12...99).100)`
`B= -9/100`
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`5.`
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`a. 4 3/7 . 8/15 + 3 4/7 . 8/15`
`= (4 3/7 + 3 4/7). 8/15`
`= (31/7 + 25/7) . 8/15`
`= 8. 8/15`
`= 64/15`
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`b. 3 1/4 : (-4/5) - 2 5/4 : (-4/5)`
`= (3 1/4- 2 5/4) : (-4/5)`
`= (13/4 - 13/4) . (-5/4)`
`= 0 . (-5/4)`
`= 0`
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`c. -2/3 : 1/4 - 2/3 : 3/4`
`= 2/3 : (-1)/4 - 2/3 : 3/4`
`= 2/3 : (-1/4 - 3/4)`
`= 2/3 : (-1)`
`= -2/3`
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`d. 5/6 . 17 1/3 - 5/6 . 47 1/3`
`= 5/6 . (17 1/3 - 47 1/3)`
`= 5/6 . (17 1/3 - 47 1/3)`
`= 5/6 . 30`
`= 25`
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`e. 11/25. (-24,8) - 11/25 . 75,2`
`= 11/25. (-24,8-75,2)`
`= 11/25. (-100)`
`= -44`
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`j. 3/14 : 1/28 - 13/21 : 1/28 + 29/42 : 1/28 - 8`
`= [(3/14 - 13/21 + 29/42) : 1/28] -8`
`= 2/7 . 28 - 8`
`= 8-8`
`= 0`
