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a) -1/24 - [ 1/4 - ( 1/2 - 7/8 )]
= -1/24 - [ 1/4 +3/8 ]
= -1/24 - 5/8
= -2/3.
a) -1/24 - [ 1/4 - ( 1/2 - 7/8 )]
= -1/24 - [ 1/4 +3/8 ]
= -1/24 - 5/8
= -2/3.
![](https://rs.olm.vn/images/avt/0.png?1311)
(-1 phần 3 + 5 phần 6 ).11-7
-1 phần 24 - [ 1 phần 4 - ( 1 phần 2 - 7 phần 8 )]
`(-1/3+5/6).11-7`
`=(-2/6+5/6).11-7`
`=-3/6*11-7`
`=-11/2-7`
`=-11/2-14/2`
`=-25/2`
`-1/24-[1/4-(1/2-7/8)]`
`=-1/24-[1/4-(4/8-7/8)]`
`=-1/24-[1/4-(-3/8)]`
`=-1/24-(2/8+3/8)`
`=-1/24-5/8`
`=-1/24-15/24`
`=-16/24==-2/3`
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\frac{3}{4}+\left(-\frac{1}{8}\right)\)
\(=\frac{6}{8}-\frac{1}{8}=\frac{5}{8}\)
b) \(-\frac{5}{12}+\left(-\frac{7}{24}\right)=\left(-\frac{10}{24}\right)+\left(-\frac{7}{24}\right)=-\frac{17}{24}\)
c) \(1+\left(-\frac{7}{8}\right)=\frac{8}{8}-\frac{7}{8}=\frac{1}{8}\)
d) \(\frac{13}{30}-\frac{1}{3}=\frac{13}{30}-\frac{10}{30}=\frac{3}{30}\)
e) \(\frac{4}{21}-\left(-\frac{5}{28}\right)=\frac{4}{21}+\frac{5}{28}=\frac{16}{84}+\frac{15}{84}=\frac{31}{84}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
`@` `\text {Ans}`
`\downarrow`
`1)`
`5/7*37 13/23 - 51 13/23*5/7`
`= 5/7* (37 13/23 - 51 13/23)`
`= 5/7* (-14)`
`= -10`
`2)`
`-2/3 +1/3+0,5+2 1/2`
`= -2/3 + 1/3 + 1/2 + 5/2`
`= (-2/3+1/3) + (1/2+5/2)`
`= -1/3 + 3`
`=8/3`
`3)`
`-0,5+2/3+1/2`
`= -1/2 + 2/3 + 1/2`
`= (-1/2 + 1/2) + 2/3`
`= 2/3`
`4)`
`(8+2 1/3-3/5) -(5+0,4)-(3 1/2 -2)`
`= 8+ 7/3 - 3/5 - 5 - 0,4 - 7/2 + 2`
`= (8+2-5) + (-3/5 - 2/5) + (7/3 - 7/2)`
`= 5 - 1 - 7/6`
`= 4 - 7/6 = 17/6`
`5)`
`(2/9-7/12):3/4+(16/9-5/12):3/4`
`= (2/9 - 7/12) \times 4/3 + (16/9 - 5/12) \times 4/3`
`= 4/3 *(2/9 - 7/12 + 16/9 - 5/12)`
`= 4/3 * [(2/9 + 16/9) + (-7/12 - 5/12)]`
`= 4/3 * ( 2 - 1)`
`= 4/3 * 1 = 4/3`
`6)`
`-(2021.0,7+19,75) +0,7- (8-19,75)`
`= -2021*0,7 -19,75 + 0,7 - 8 + 19,75`
`= 0,7*(-2021 + 1) - 8`
`= -1414-8`
`= -1422`
`7)`
`15/34+7/21+19/34-20/15`
`= (15/34 + 19/34) + 7/21 - 20/15`
`= 1 + 7/21 - 20/15`
`= 4/3 - 20/15 =0`
`8)`
`2 5/6+1/6:(-5/8)`
`= 17/6 + (-4/15)`
`= 77/30`
`9)`
`(-2)^2 +2/9. (4/5-2/3)`
`= 4 + 2/9*2/15`
`= 4+4/135`
`= 544/135`
`10)`
`(-1/5+3/7):5/4+(-4/5+4/7):5/4`
`= (-1/5+3/7) * 4/5 + (-4/5+4/7) * 4/5`
`= 4/5*(-1/5 +3/7-4/5+4/7)`
`= 4/5*[(-1/5-4/5)+(3/7+4/7)]`
`= 4/5* (-1+1)`
`= 4/5*0=0`
`11)`
`2022,2021 . 1954,1945+ 2022,2021 . (-1954,1945)`
`= 2022,2021 * [1954,1945 + (-1954,1945)]`
`= 2022,2021*0 `
`= 0`
`12)`
`-5,2 .72 +69,1 +5,2 . (-28)+(-1,1)`
`= -5,2*72 + 69,1 - 5,2*28 - 1,1`
`= -5,2*(72+28) + (69,1 - 1,1)`
`= -5,2*100 + 68`
`= -520 + 68`
`= -452`
`13)`
`(7 -1/2-3/4) : (5-1/4-5/8)`
`= 23/4 \div 33/8`
`=46/33`
`14)`
`(8+ 2 1/3 -3/5) -(5+0,4) -( 3 1/3 - 2)`
`= 8+ 2 1/3 - 3/5 - 5 - 0,4 - 3 1/3 + 2`
`= (8+2-5) + (2 1/3 - 3 1/3) - (0,6 + 0,4) `
`= 5 - 1 - 1`
`= 3`
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 3/4 + -1/8 = 5/8
b)-5/12 + -7/24 = -9/8
c) 4/21 - -5/28 = 31/84
d) 1 + -7/28 = 3/4
e) -4/3 - 17/6= -25/6
f) 1/3 - ( 1/2 +1/8 )= -7/24
g)1/21 - ( 1/7 - 1/3 ) = 5/21
h)1/2 - 1/4 + 1/13 + 1/8= 47/104
a) x - 1/10 = 1/15
x=1/15+1/10
x=1/6 Vay x=1/6b) -4/21 - x = -3/7
x=-4/21+3/7 x=5/21 Vay x=5/21c) x + 1/2 = 3/4 - (-1/2)
x+1/2= 5/4
x= 5/4-1/2
x=3/4
Vay x=3/4
d) 4/7 - x = 1/3 - (-2/3)
x= 4/7-1/3-2/3 x= -3/7 Vay x=-3/7![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\frac{x}{24}=-\frac{7}{8}\)
\(\Rightarrow x=-\frac{7}{8}.24=-7.3=-21\)
b) \(x+\frac{3}{x}-4=\frac{9}{8}\)
\(\Rightarrow\frac{x^2+3}{x}=\frac{9}{8}+\frac{32}{8}=\frac{41}{8}\)
\(\Rightarrow8x^2+24=41x\)
Liệu bạn có viết sai đề không nhỉ? Phần này nghiêng về lớp 8 hơn
\(x+\frac{7}{5}=x-\frac{1}{7}\)
\(\Rightarrow\frac{7}{5}=-\frac{1}{7}\)
⇒ Không có giá trị của x tmđb
P/s : Bạn check lại đề + viết rõ yêu cầu đề dùm :>>
\(...-\dfrac{1}{24}-\left[\dfrac{1}{4}--\dfrac{3}{8}\right]=-\dfrac{1}{24}-\dfrac{5}{8}=-\dfrac{2}{3}\)
\(-\dfrac{1}{24}-\left[\dfrac{1}{4}-\left(\dfrac{1}{2}-\dfrac{7}{8}\right)\right]\)
\(=-\dfrac{1}{24}-\left[\dfrac{1}{4}-\left(\dfrac{4}{8}-\dfrac{7}{8}\right)\right]\)
\(=-\dfrac{1}{24}-\left(\dfrac{1}{4}+\dfrac{3}{8}\right)\)
\(=-\dfrac{1}{24}-\left(\dfrac{2}{8}+\dfrac{3}{8}\right)\)
\(=-\dfrac{1}{24}-\dfrac{5}{8}\)
\(=-\dfrac{1}{24}-\dfrac{15}{24}\)
\(=\dfrac{-16}{24}\)
\(=-\dfrac{2}{3}\)