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\(a,\frac{7}{25}\cdot\frac{39}{-14}\cdot\frac{50}{78}=\frac{7}{25}\cdot-\frac{39}{14}\cdot\frac{25}{39}=-\frac{7}{14}=-\frac{1}{2}\)
\(b,\left(\frac{3}{8}+-\frac{3}{4}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}\)
\(=\frac{5}{24}:\frac{5}{6}+\frac{1}{2}=\frac{1}{4}+\frac{1}{2}=\frac{6}{8}=\frac{3}{4}\)
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39.50 + 25.39 + 75.61 = 39. ( 50 +25) + 75.61
= 39.75 + 75.61
= 75. ( 39 + 61 )
= 75 . 100 = 7500
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g) 51 . ( -35 ) + ( -51 ) . ( -65 )
= ( -51 ) . 35 + ( -51 ) . ( -65 )
= ( -51 ) . ( -65 + 35 )
= ( -51 ) . ( -30 )
= 1530
k) ( 6 . 8 - 10 : 5 ) + 3 . ( -7 )
= ( 48 - 2 ) + ( -21 )
= 46 + ( -21 )
= 25
s) 1 - 2 - 3 + 4 + 5 - 6 - 7 + 8 + 9 - ... - 2007 + 2008 + 2009
= ( 1 - 2 - 3 + 4 ) + ( 5 - 6 - 7 + 8 ) + ... + ( 2005 - 2006 - 2007 + 2008 ) + 2009
= 0 + 0 + ... + 0 + 2009
= 2009
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1: \(\left(-5\right)+8-7=8+\left(-5-7\right)\)
=-12+8
=-4
2: \(\left(-8\right)+2+8=\left(-8+8\right)+2=0+2=2\)
3: \(\left(-1\right)+3+1\)
\(=\left(-1+1\right)+3\)
=0+3
=3
4: \(\left(-6\right)+8-14\)
\(=\left(-6-14\right)+8\)
=-20+8
=-12
5: \(\left(-4\right)+3-7\)
\(=\left(-4-7\right)+3\)
=-11+3
=-8
6: \(\left(-4\right)+5-2\)
\(=\left(-4-2\right)+5\)
=-6+5
=-1
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19: \(\left(-17\right)+7-10\)
\(=\left(-17+7\right)-10\)
=-10-10
=-20
20: \(\left(-18\right)+10+8\)
\(=\left(-18\right)+\left(10+8\right)\)
=-18+18
=0
21: \(\left(-20\right)+15+5\)
\(=\left(-20\right)+\left(15+5\right)\)
=-20+20
=0
22: \(\left(-16\right)+8+8\)
\(=\left(-16\right)+\left(8+8\right)\)
=-16+16
=0
23: \(\left(-6\right)+3-3\)
\(=\left(-6\right)+\left(3-3\right)\)
=-6+0
=-6
24: \(13+3-16\)
\(=\left(13+3\right)-16\)
=16-16
=0
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Ta có \(\frac{-17}{30}-\frac{-11}{15}-\frac{7}{12}\)
\(=\frac{-17}{30}+\frac{11}{15}-\frac{7}{12}\)
\(=\left(\frac{-17}{30}+\frac{22}{30}\right)-\frac{7}{12}\)
\(=\frac{1}{6}-\frac{7}{12}=\frac{2}{12}-\frac{7}{12}=-\frac{5}{12}\)
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a) 20,7 + 1,47 : 7 – 0,23.5
= 20,7 + 0,21 – 1,15
= 20,91 – 1,15
= 19,76
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a)29 . (19 – 13) – 19 . (29 – 13)
= 29 . 6 – 19 . 16
= 174 – 304
= –130.
b)31.(-18)+31.(-81)-31
= 31. [-18 + (-81) - 1 ]
= 31. (-100)
= -3100
c)(7.3-3):(-6)
(7.3-3):(-6)
= (21-3):(-6)
= 18 : (-6)
= 3
d)72:[(-6).2+4)]
= 72 : ( -12 + 4 )
= 72 : -8
= -9
\(A=\frac{-7}{25}.\frac{39}{-14}.\frac{35}{91}\)
\(A=\frac{-7.39.35}{25.\left(-14\right).91}\)
\(A=\frac{1.39.7}{5.2.91}\)
\(A=\frac{273}{910}=\frac{3}{10}\)
\(A=\frac{-7}{25}.\frac{39}{-14}.\frac{35}{91}\)
\(A=\frac{-7.39.35}{25.\left(-14\right).91}\)
\(A=\frac{1.39.7}{5.5.91}\)( bc này bạn chỉ cần rút gọn mấy số chia heét cho nhau là xong nhé )
\(A=\frac{273}{910}\)
\(A=\frac{3}{10}\)
Ps : Đừng ai bảo t copy nhé , mệt lắm