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***c,4(x-5)-3(x+7)=-19
Suy ra (4x-20)-(3x+21)=-19
Suy ra (4x-3x)-(20+21)=-19
Suy ra x-41=-19
suy ra x=-19+41
Suy ra x=22
Vậy x=22
![](https://rs.olm.vn/images/avt/0.png?1311)
a)=>x=13+3/5=68/5.
Vậy x = 68/5
b)=>x/6=5/7+-23/42
=>x/6=1/6
=>x=1
Vậy x=1
còn lại tự làm nha😆😆😆😆😆
a) x-3/5=13
suy ra x=13+3/5
suy ra x=68/5
suy ra x=13.6
b)x/6=5/7+23/-42
suy ra x/6=1/6
suy ra x=1
d) x+11/12=2/5
suy ra x=2/5-11/12
suy ra x=-31/60
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\(\frac{12}{7}\times\frac{2}{11}+\frac{12}{11}\times\frac{15}{7}-\frac{12}{7}\times\frac{6}{11}\)
\(=\frac{12}{7}\times\frac{2}{11}+\frac{12}{7}\times\frac{15}{11}-\frac{12}{7}\times\frac{6}{11}\)
\(=\frac{12}{7}\times\left(\frac{2}{11}+\frac{15}{11}-\frac{6}{11}\right)\)
\(=\frac{12}{7}\times1=\frac{12}{7}\)
\(\frac{12}{7}.\frac{2}{11}+\frac{12}{11}.\frac{15}{7}-\frac{12}{7}.\frac{6}{11}\)
= \(\frac{24}{77}\)+\(\frac{180}{77}\)-\(\frac{72}{77}\)
=\(\frac{132}{77}\)
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a) x - (11 - x) = -48 + (-12 + x)
x - 11 + x = -48 + (-12) + x
x + x - x = -48 + (-12) + 11
x + 0 = (-60) + 11
x = -49
b) (15 - x) + (x - 12) = 7 - (-8 + x)
15 - x + x - 12 = 7 + 8 + x
15 - x + x - 12 = 15 + x
x + x - x = 15 - 15 + 12
x + 0 = 0 + 12
x = 12
c) (x - 12) - (2x + 31) = -6 - 5
x - 12 - 2x - 31 = -1
x - 12 - 2x = -1 + 31
x - 12 - 2x = 30
x - 2x = 30 + 12
-1x = 42
=> x = -42
d) |x + 5| - (-17) = 20
=> |x + 5| + 17 = 20
=> |x + 5| = 20 - 17
=> |x + 5| = 3
=> \(\orbr{\begin{cases}x+5=3\\x+5=-3\end{cases}}\)
=> \(\orbr{\begin{cases}x=3-5\\x=-3-5\end{cases}}\)
=> \(\orbr{\begin{cases}x=-2\\x=-8\end{cases}}\)
12x2 - 3x = 0
=> 12x2 - 3x = (22 . 3x2) - 3x = 0
=> 3x . (4x - 1) = 0
=> 3x . 4x - 3x . 1 = 0
=> 3x . 4x - 3x = 0
=> 12x - 3x = 0
=> 4x =0
=> x = 0
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Bài 1:
a: \(x=\dfrac{2}{3}:\dfrac{3}{5}=\dfrac{2}{3}\cdot\dfrac{5}{3}=\dfrac{10}{9}\)
b: \(x=\dfrac{17}{8}:\dfrac{7}{17}=\dfrac{17}{8}\cdot\dfrac{17}{7}=\dfrac{289}{56}\)
c: \(x=-\dfrac{3}{4}:\dfrac{7}{12}=\dfrac{-3}{4}\cdot\dfrac{12}{7}=\dfrac{-63}{28}=-\dfrac{9}{4}\)
d: \(\Leftrightarrow x\cdot\dfrac{1}{6}=\dfrac{3}{8}-\dfrac{1}{4}=\dfrac{1}{4}\)
hay \(x=\dfrac{1}{4}:\dfrac{1}{6}=\dfrac{3}{2}\)
e: \(\Leftrightarrow\dfrac{1}{2}:x=-4-\dfrac{1}{3}=-\dfrac{17}{3}\)
hay \(x=-\dfrac{1}{2}:\dfrac{17}{3}=\dfrac{-3}{34}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài làm
m) (x + 2).(3 - x) = 0;
=> x + 2 = 0 hoặc 3 - x = 0
=> x = -2 hoặc x = 3
Vậy x = -2 hoặc x = 3
d) 511.712 + 511.711
= 511 . ( 712 + 711 )
= 511 . [ 711 . ( 7 + 1 ) ]
= 511 . 711 . 8
= ( 5 . 7 )11 . 8
= 3511 . 8
512.712 + 9.511.711
= 511 ( 5 . 712 + 9 . 1 . 711 )
= 511 [ 711 ( 5 . 7 + 9 . 1 . 1 ) ]
= 511 ( 711 . 44 )
= 511 . 711 . 44
= 3511 . 44
m. \(\left(x+2\right)\left(3-x\right)=0\Leftrightarrow\orbr{\begin{cases}x+2=0\\3-x=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=-2\\x=3\end{cases}}\)
d. \(\frac{5^{11}.7^{12}+5^{11}.7^{11}}{5^{12}.7^{12}+9.5^{11}.7^{11}}=\frac{5^{11}.\left(7^{12}+7^{11}\right)}{5^{11}.\left(5.7^{12}+9.7^{11}\right)}=\frac{7^{12}+7^{11}}{5.7^{12}+9.7^{11}}=\frac{1}{5.9}=\frac{1}{45}\)
q. \(\left(x-3\right)+\left(x-2\right)+\left(x-1\right)+...+10+11=11\)
\(\Rightarrow\left(x-3\right)+\left(x-2\right)+\left(x-1\right)+...+10=0\)
\(\Rightarrow\left[\left(x-3\right)+\left(x-2\right)+\left(x-1\right)\right]+(1+2+3+...+10)=0\)
\(\Rightarrow\left(x-3\right)+\left(x-2\right)+\left(x-1\right)+55=0\)
\(\Rightarrow x-3+x-2+x-1=-55\)
\(\Rightarrow3x-6=-55\)
\(\Rightarrow3x=-49\)
\(\Rightarrow x=-\frac{49}{3}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{4}{5}\)+ \(\frac{1}{5}\): \(\frac{-2}{15}\)= \(\frac{4}{5}\)+ \(\frac{1}{5}\)* \(\frac{-15}{2}\)=\(\frac{4}{5}\) + \(\frac{-3}{2}\)= \(\frac{-7}{10}\)
b = \(\frac{-7}{12}\). (\(\frac{3}{11}\)+ \(\frac{-14}{11}\)) + \(\frac{5}{6}\)= \(\frac{-7}{12}\). (-1) + \(\frac{5}{6}\)= \(\frac{7}{12}\)+ \(\frac{10}{12}\)= \(\frac{17}{12}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)x-(11-x)=48+(-12+x) b)(15-x)+(x-12)=7-(-8+x)
x-11+x =48-12+x 15-x+x-12 =7+8-x
2x-11 =36+x 3 =15-x
x-11 =36 x =15-3
x =36+11 x =12
x 47
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