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a) x= \(\frac{-5}{12}\)
b) x = \(\frac{2}{5}\)
c) x =\(\frac{-87}{140}\)
d) x = \(\frac{109}{140}\)
e) x = \(\frac{13}{63}\)
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Bài 2:
a, \(\dfrac{5}{23}\) \(\times\) \(\dfrac{17}{26}\) + \(\dfrac{5}{23}\) \(\times\) \(\dfrac{9}{26}\)
= \(\dfrac{5}{23}\) \(\times\) ( \(\dfrac{17}{26}\) + \(\dfrac{9}{26}\))
= \(\dfrac{5}{23}\) \(\times\) \(\dfrac{26}{26}\)
= \(\dfrac{5}{23}\)
b, \(\dfrac{3}{4}\) \(\times\) \(\dfrac{7}{9}\) + \(\dfrac{7}{4}\) \(\times\) \(\dfrac{3}{9}\)
= \(\dfrac{7}{12}\) + \(\dfrac{7}{12}\)
= \(\dfrac{14}{12}\)
= \(\dfrac{7}{6}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
1, 2x - 35 = 15
2x = 15 + 35
2x = 50
x = 50 : 2
x = 25.
2, 3x + 18 = 12
3x = 12 - 18
3x = -6
x = -6 : 3
x = -2.
3, / x - 1 / = 0
=> x \(\in\varnothing\).
4, -13 /x/ = - 26
/x/ = -26 : -13
=> \(\orbr{\begin{cases}x=2\\x=-2\end{cases}}\)
Vậy x \(\in\){ 2 ; -2}.
5,4 - ( 27 - 3 ) = x - ( 13 - 4 )
4 - 24 = x - 9
-20 = x - 9
-x = 9 + 20
-x = 29
x = -29.
6, 47 - ( x + 15 ) = 21
47 - x - 15 = 21
-x - 15 = 21 - 47
-x - 15 = -26
-x = -26 + 15
-x = - 11
x = 11.
7, -5 -( 24 - x) = - 11
-5 - 24 + x = -11
-24 + x = -11 + 5
-24 + x = -6
x = -6 + 24
x = 18.
8, 6 - /x/ = 2
/x/ = 6 - 2
\(\orbr{\begin{cases}x=3\\x=-3\end{cases}}\)
Vậy x \(\in\left\{3;-3\right\}.\)
9, 6 + /x/ = 2
/x/ = 2 - 6
=> x = -4.
2x - 35 = 15
=> 2x = 15 + 35
=> x = 50 : 2
=> x = 25
3x + 18 = 12
=> 3x = 12 - 18
=> x = ( -6 ) : 3
=> x = -2
| x - 1 | = 0
=> x - 1 = 0
=> x = 0 + 1
=> x = 1
-13 * | x | = -26
=> | x | = -26 : ( -13 )
=> | x | = 2
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\(\frac{x}{\frac{1}{2}}+\frac{x}{\frac{1}{3}}+x=42\)
\(\Rightarrow\frac{x}{\frac{3}{6}}+\frac{x}{\frac{2}{6}}+\frac{x}{\frac{6}{6}}=42\)
\(\Rightarrow\frac{x}{\frac{3}{6}+\frac{2}{6}+\frac{6}{6}}=42\)
\(\Rightarrow\frac{x}{\frac{11}{6}}=42\)
\(\Rightarrow x=77\)
\(x.\frac{4}{7}+x.\frac{2}{3}+x.\frac{3}{7}=\frac{11}{5}\)
\(\Rightarrow x.\left(\frac{4}{7}+\frac{3}{7}+\frac{2}{3}\right)=\frac{11}{5}\)
\(\Rightarrow x.\frac{5}{3}=\frac{11}{5}\)
\(\Rightarrow x=\frac{33}{25}\)
\(\left(\frac{31}{5}-x\right):\frac{2}{3}=\frac{7}{6}\)
\(\Rightarrow\frac{31}{5}-x=\frac{7}{9}\)
\(\Rightarrow x=\frac{244}{45}\)
\(\frac{4}{3}+\left(x-\frac{3}{5}\right)=\frac{21}{2}\)
\(\Rightarrow\frac{4}{3}+x-\frac{3}{5}=\frac{21}{2}\)
\(\Rightarrow x+\frac{11}{5}=\frac{21}{2}\)
\(\Rightarrow x=\frac{83}{10}=8,3\)
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Bài 1 : Tính bằng cách thuận tiện
A = 3/13 x 5/7 + 2/13 x 3/7
= 2/13 + 1/13 x 5/7 + 2/13 x 3/7
= 2/13 x 72/91 + 2/13 x 3/7
= 2/13 x ( 72/91 + 3/7 )
= 2/13 x 37/24
= 37/156.
B = 21/22 x 17/8 + 21/8 x 7/22
= 21/22 x 17/8 + 17/8 + 4/8 x 7/22
= 21/22 x 17/8 + 17/8 x 7/44
= ( 21/22 + 7/44 ) x 21/22
= 31/44 x 21/22
= 651/968.
Chúc bạn học tốt!!!
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a. 25,97 + 6,54 + 103,46
= 25,97 + (6,54+103,46)
= 25,97+110
= 135,97
b. 50% + 7/12-1/2
= 1/2+7/12-1/2
= (1/2-1/2)+7/12
= 0+7/12
= 7/12
c. 2015.65 + 2015.45 - 2015.10
= 2015. (65+45-10)
= 2015.100
= 201500
2.a.2/3.x+3/4=3
=> 2/3.x=3-3/4
=> 2/3.x=9/4
=> x=9/4:2/3
=> x=9/4.3/2
=> x=27/8
b. 100-7(x-5)=58
=> 7(x-5)=100-58
=> 7(x-5)=42
=> x-5=42:7
=> x-5=6
=> x=6+5
=> x=11
c. x+1/3=7/26 x 13/6
=> x+1/3 = 7/12
=> x=7/12-1/3
=> x=7/12-4/12
=> x=3/12
=> x=1/4
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Bài 1: Ta có: \(4\dfrac{3}{5}+\dfrac{7}{10}< X< \dfrac{20}{3}\)
\(\dfrac{23}{5}+\dfrac{7}{10}< X< \dfrac{20}{3}\)
\(\dfrac{138}{30}< X< \dfrac{200}{3}\)
\(\Rightarrow X\in\left\{\dfrac{160}{30};\dfrac{161}{30};\dfrac{162}{30};...;\dfrac{198}{30};\dfrac{199}{30}\right\}\)
Bài 2: \(X-2019\dfrac{2}{13}=3\dfrac{7}{26}+4\dfrac{7}{52}\)
\(\Rightarrow X-\dfrac{26249}{13}=\dfrac{85}{26}+\dfrac{215}{52}\)
\(\Rightarrow X-\dfrac{26249}{13}=\dfrac{385}{52}\)
\(\Rightarrow X=\dfrac{105381}{52}\)
a. 60/169
b. 35/24
c.32/42
a) \(x:\frac{5}{13}+\frac{2}{26}=1\)
\(x:\frac{5}{13}=1-\frac{2}{26}\)
\(x:\frac{5}{13}=\frac{12}{13}\)
\(x=\frac{12}{13}\times\frac{5}{13}\)
\(x=\frac{60}{169}\)
b) \(x\times\frac{3}{5}=\frac{7}{8}\)
\(x=\frac{7}{8}:\frac{3}{5}\)
\(x=\frac{35}{24}\)
c) \(x=\frac{3}{7}+\frac{4}{21}+\frac{5}{42}\)
\(x=\frac{3\times6}{7\times6}+\frac{4\times2}{21\times2}+\frac{5}{42}\)
\(x=\frac{18}{42}+\frac{8}{42}+\frac{5}{42}=\frac{31}{42}\)