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\(-4\dfrac{1}{5}-x=2,25\)
\(\dfrac{-21}{5}-x=2,25\)
-4.2-x=2,25
x=-4,2-2,25
x=-6,45
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 2,25 : \(\frac{-6}{25}=\frac{9}{4}\cdot\frac{-25}{6}=\frac{9\cdot\left(-25\right)}{4\cdot6}=\frac{3\cdot3\cdot\left(-25\right)}{4\cdot3\cdot2}=\frac{-75}{8}\)
b) \(\frac{2^3\cdot5^2\cdot7^2\cdot3^7}{49\cdot5^3\cdot3^6\cdot11}=\frac{2^3\cdot5^2\cdot7^2\cdot3^6\cdot3}{7^2\cdot5^2\cdot5\cdot3^6\cdot11}=\frac{2^3\cdot3}{5\cdot11}=\frac{24}{55}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{28,8:13\frac{5}{7}+6,6:\frac{2}{3}}{1\frac{11}{16}:}2,25\)=\(\frac{\frac{21}{10}+\frac{99}{10}}{\frac{3}{4}}=\frac{12}{\frac{3}{4}}=16\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 2/7 + x = -0,75
x= - 3/4 - 2/7
x= 21/28 - 8/28
x = 13/28
Vậy x = 13/28
b) -4 1/5 - x = 2,25
-21/5 - x = 2,25
-x = 2,25 + 21/5
-x = 45/20 + 21/5
-x = 45/20 + 84/20
-x = 84/20
x = -84/20
Vậy x = -84/20
c) x : 8,5 = -2,2
x = -2,2 . 8,5
x = -18,7
Vậy x = -18,7
d) ( 2x/5 - 1 ) : ( -5 ) = 1/7
2x/5 - 1 = 1/7 . ( -5 )
2x/5 - 1 = -5/7
2x/5 = -5/7 + 1
2x/5 = -5/7 + 7/7
2x/5 = 2/7
x = 2/7 : 2/5
x = 2/7 . 5/2
x = 5/7
Vậy x = 5/7
![](https://rs.olm.vn/images/avt/0.png?1311)
a.\(\frac{-4}{5}-x=2,25\Leftrightarrow\frac{-4}{5}-x=\frac{9}{4}\Leftrightarrow x=\frac{-61}{20}\)
b. \(\left(\frac{2x}{5}-1\right)\times\frac{-1}{5}=\frac{1}{7}\Leftrightarrow\frac{-2x}{25}+\frac{1}{5}=\frac{1}{7}\Leftrightarrow\frac{-2x}{25}=\frac{-2}{35}\Leftrightarrow x=\frac{5}{7}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(2,25:\dfrac{-6}{25}=\dfrac{9}{4}:\dfrac{-6}{25}\\ =-\dfrac{9}{4}\cdot\dfrac{25}{6}=-\dfrac{3}{4}\cdot\dfrac{25}{2}\\ =-\dfrac{75}{8}\)
\(2.25:\dfrac{-6}{25}\) = \(\dfrac{9}{4}:\dfrac{-6}{25}=\dfrac{9}{4}.\dfrac{25}{-6}=\dfrac{3}{4}.\dfrac{25}{-2}=\dfrac{75}{-8}=\dfrac{-75}{8}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Giải:
a) \(\left(\dfrac{1}{3}.x\right):\dfrac{2}{3}=1\dfrac{3}{4}:\dfrac{2}{5}\)
\(\Leftrightarrow\left(\dfrac{1}{3}x\right):\dfrac{2}{3}=\dfrac{7}{4}:\dfrac{2}{5}\)
\(\Leftrightarrow\left(\dfrac{1}{3}x\right):\dfrac{2}{3}=\dfrac{35}{8}\)
\(\Leftrightarrow\dfrac{1}{3}x=\dfrac{35}{8}.\dfrac{2}{3}\)
\(\Leftrightarrow\dfrac{1}{3}x=\dfrac{35}{12}\)
\(\Leftrightarrow x=\dfrac{35}{12}:\dfrac{1}{3}\)
\(\Leftrightarrow x=\dfrac{35}{4}\)
Vậy \(x=\dfrac{35}{4}\).
b) \(4,5:0,3=2,25\left(0,1.x\right)\)
\(\Leftrightarrow15=2,25\left(0,1.x\right)\)
\(\Leftrightarrow2,25\left(0,1.x\right)=15\)
\(\Leftrightarrow0,1.x=\dfrac{15}{2,25}\)
\(\Leftrightarrow0,1.x=\dfrac{20}{3}\)
\(\Leftrightarrow x=\dfrac{20}{3}:0,1\)
\(\Leftrightarrow x=\dfrac{200}{3}\)
Vậy \(x=\dfrac{200}{3}\).
c) \(8:\left(\dfrac{1}{4}.x\right)=2:0,02\)
\(\Leftrightarrow8:\left(\dfrac{1}{4}.x\right)=100\)
\(\Leftrightarrow\dfrac{1}{4}.x=\dfrac{2}{25}\)
\(\Leftrightarrow x=\dfrac{2}{25}:\dfrac{1}{4}\)
\(\Leftrightarrow x=\dfrac{8}{25}\)
Vậy \(x=\dfrac{8}{25}\).
d) \(3:2\dfrac{1}{4}=\dfrac{3}{4}:\left(6.x\right)\)
\(\Leftrightarrow3:\dfrac{9}{4}=\dfrac{3}{4}:\left(6.x\right)\)
\(\Leftrightarrow\dfrac{4}{3}=\dfrac{3}{4}:\left(6.x\right)\)
\(\Leftrightarrow\dfrac{4}{3}:\left(6.x\right)=\dfrac{3}{4}\)
\(\Leftrightarrow6.x=\dfrac{4}{3}:\dfrac{3}{4}\)
\(\Leftrightarrow6.x=\dfrac{16}{9}\)
\(\Leftrightarrow x=\dfrac{16}{9}:6\)
\(\Leftrightarrow x=\dfrac{8}{27}\)
Vậy \(x=\dfrac{8}{27}\).
Chúc bạn học tốt!!!
= 2,25 x ( 48 : 0,125)
= 2,25 x 384
= 864