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\(xy-2x+y=1\)
\(\Leftrightarrow xy-2x+y-2=1-2\)
\(\Leftrightarrow x\left(y-2\right)+y-2=-1\)
\(\Leftrightarrow\left(y-2\right)\left(x+1\right)=-1\)
Ta có bảng:
y-2 | -1 | 1 |
x+1 | 1 | -1 |
y | 1 | 3 |
x | 0 | -2 |
Vậy \(\left(x;y\right)=\left(0;1\right);\left(-2;3\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(27-\left(14-x\right)=-x+3\)
\(\Leftrightarrow\)\(27-14+x=-x+3\)
\(\Leftrightarrow\)\(13+x=-x+3\)
\(\Leftrightarrow\)\(2x=-10\)
\(\Leftrightarrow\)\(x=-5\)
Vậy...
Câu 1 :
=> 27-14+x = -x+3
=> 13+x = -x+3
=> x = -x+3-13 = -x-10
=> 10 = -x-x = -2x
=> x = 10 : (-2) = -5
Vậy x = -5
Tk mk nha
![](https://rs.olm.vn/images/avt/0.png?1311)
\(C=5\frac{9}{10}:\frac{3}{2}-\left(2\frac{1}{3}.4\frac{1}{2}-2.2\frac{1}{3}\right):\frac{7}{4}\)
\(=\frac{59}{10}:\frac{3}{2}-\left(\frac{7}{3}.\frac{9}{2}-2.\frac{7}{3}\right):\frac{7}{4}\)
\(=\frac{59}{15}-\left[\frac{7}{3}\left(\frac{9}{2}-2\right)\right]:\frac{7}{4}\)
\(=\frac{59}{15}-\frac{35}{6}:\frac{7}{4}\)
\(=\frac{59}{15}-\frac{10}{3}\)
\(=\frac{9}{15}=\frac{3}{5}\)
\(\cdot62,87+35,14+4,13+8,35+4,86+5,65\)
\(=\left(62,87+4,13\right)+\left(35,14+4,86\right)+\left(8,35+5,65\right)\)
\(=67+40+14\)
\(=121\)
![](https://rs.olm.vn/images/avt/0.png?1311)
1: Ta có: \(20-2\left(x+4\right)=4\)
\(\Leftrightarrow2\left(x+4\right)=16\)
\(\Leftrightarrow x+4=8\)
hay x=4
5: Ta có: \(\left(x+1\right)^3=27\)
\(\Leftrightarrow x+1=3\)
hay x=2
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có : \(\frac{1}{2}+\frac{1}{14}+\frac{1}{35}+...+\frac{1}{x\left(x+3\right):2}=\frac{9}{14}\)
\(\Rightarrow2\left(\frac{1}{4}+\frac{1}{28}+\frac{1}{70}+...+\frac{1}{x\left(x+3\right)}\right)=\frac{9}{14}\)
\(\Rightarrow2.\frac{1}{3}\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{x\left(x+3\right)}\right)=\frac{9}{14}\)
\(\Rightarrow\frac{2}{3}\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{x}-\frac{1}{x+3}\right)=\frac{9}{14}\)
\(\Rightarrow1-\frac{1}{x+3}=\frac{27}{28}\)
\(\Rightarrow\frac{1}{x+3}=\frac{1}{28}\)
=> x + 3 = 28
=> x = 25
1/ -8+13-...+x=250
2/ 1-3+5-7+...-x=-600
3/ -2+4-6+8-...+x=100
4/ 2-6=10-14+...-x=-800
giúp mình với nha
![](https://rs.olm.vn/images/avt/0.png?1311)
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\(\dfrac{-2}{3}\left(x-\dfrac{1}{4}\right)=\dfrac{1}{3}\left(2x-1\right)\)
\(\Leftrightarrow\dfrac{-2}{3}x+\dfrac{1}{6}=\dfrac{2}{3}x-\dfrac{1}{3}\)
\(\Leftrightarrow\dfrac{-2}{3}x-\dfrac{2}{3}x=\dfrac{-1}{3}-\dfrac{1}{6}\)
\(\Leftrightarrow\dfrac{-4}{3}x=\dfrac{-1}{2}\)
\(\Leftrightarrow x=\dfrac{3}{8}\)
Vậy \(x=\dfrac{3}{8}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a: =152,3+7,7+2021,19-2021,19
=160
b: =7/15*3/14*20/13
\(=\dfrac{7}{14}\cdot\dfrac{3}{15}\cdot\dfrac{20}{13}=\dfrac{1}{2}\cdot\dfrac{1}{5}\cdot\dfrac{20}{13}=\dfrac{2}{13}\)
c: \(=\dfrac{7}{4}\left(\dfrac{13}{12}-\dfrac{10}{12}\right)+\dfrac{5}{6}=\dfrac{7}{16}+\dfrac{5}{6}=\dfrac{61}{48}\)
\(4\left(x+1\right)-\left(3x+1\right)=14\)
\(\Leftrightarrow\)\(4x+4-3x-1=14\)
\(\Leftrightarrow\)\(x+3=14\)
\(\Leftrightarrow\)\(x=11\)
Vậy....