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a) `123 - 27 + 27 + 13 - 123`
`= (123 - 123) + (27 - 27) + 13`
`= 0 + 0 + 13`
`= 13`
`---`
b) `175 + 25 + 13 + 15 - 175 - 25`
`= (175-175)+(25-25)+25+13`
`=0+0+25+13`
`=28`
`---`
c) \(53\times39+47\times39+53\times21+47\times21\)
\(=\text{[}\left(53+47\right)\times39]+\left[\left(53+47\right)\times21\right]\)
\(=\left(100\times39\right)+\left(100\times21\right)\)
\(=3900+2100\)
`=6000`
`---`
d) \(49\times35+49\times16-49\times61\)
`=` \(49\times\left(35+16-61\right)\)
`=` \(49\times\left(-10\right)\)
`=-490`
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 27-(-15)-2 =27+15-2
=40
b)(-12)+35-8=23-8
= 15
c)x + 37 + ( -17 ) + 25=x +20+25
=x+45
d) ( -66 ) - ( y - 16 ) + 150=66-y+16 +150
=66-y+166
=66+166-y
= 232+y
k mình nha!Chúc bạn học tốt!!!!^-^
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1) Ta có: \(3\left(x-1\right)-5\left(x-2\right)=4\left(x+1\right)\)
\(\Leftrightarrow3x-5-5x+10-4x-4=0\)
\(\Leftrightarrow-6x+1=0\)
\(\Leftrightarrow-6x=-1\)
hay \(x=\dfrac{1}{6}\)
2) Ta có: \(-2\left(x-2\right)-4\left(x+1\right)=-3\left(x+3\right)\)
\(\Leftrightarrow-2x+4-4x-4+3x+9=0\)
\(\Leftrightarrow-3x=-9\)
hay x=3
3) Ta có: \(3x^2+2x=0\)
\(\Leftrightarrow x\left(3x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-\dfrac{2}{3}\end{matrix}\right.\)
4) Ta có: \(x^2-5x=0\)
\(\Leftrightarrow x\left(x-5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=5\end{matrix}\right.\)
5) Ta có: \(\left(2x-3\right)^2=36\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-3=6\\2x-3=-6\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2x=9\\2x=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{9}{2}\\x=-\dfrac{3}{2}\end{matrix}\right.\)
6) Ta có: \(\left(5x-1\right)^3=125\)
\(\Leftrightarrow5x-1=5\)
\(\Leftrightarrow5x=6\)
hay \(x=\dfrac{6}{5}\)
7) Ta có: \(3^{x+1}=27\)
\(\Leftrightarrow x+1=3\)
hay x=2
![](https://rs.olm.vn/images/avt/0.png?1311)
1: Ta có: \(2155-\left(174+2155\right)+\left(-68+174\right)\)
\(=2155-174-2155-68+174\)
=-68
2) Ta có: \(-25\cdot72+25\cdot21-49\cdot25\)
\(=-25\cdot\left(72-21+49\right)\)
\(=-25\cdot100=-2500\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 22 + (2x -13) = 83 => 2x -13 = 61 => x = 37.
b) 51 - (-12 + 3x) = 27 => 63 - 3x = 27 => x = 12.
c) - (2x + 2) + 21 = - 23 => 2x + 2 = 44 => x = 21.
d) 25 - (25 - x) = 0 => 25 - 25 + x = 0 => x = 0.
![](https://rs.olm.vn/images/avt/0.png?1311)
a: \(\left(-10\right)\cdot35+10\cdot\left(-12\right)-\left(-10\right)\)
\(=\left(-10\right)\cdot35+\left(-10\right)\cdot12-\left(-10\right)\)
\(=-10\left(35+12-1\right)=-10\cdot46=-460\)
b: \(20\cdot\left(-345\right)+\left(-20\right)\cdot\left(-315\right)\)
\(=20\cdot\left(-345\right)+20\cdot315\)
\(=20\left(-345+315\right)=-30\cdot20=-600\)
c: \(25\left(27-55\right)-27\left(25-55\right)\)
\(=25\cdot27-25\cdot55-27\cdot25+27\cdot55\)
\(=27\cdot55-25\cdot55=2\cdot55=110\)
d: \(25\cdot\left(-415\right)+9\cdot\left(-15\right)\cdot418\)
\(=-25\cdot415-9\cdot15\cdot418\)
\(=-5\left(5\cdot415+3\cdot9\cdot418\right)\)
\(=-5\left(2075+11286\right)=-5\cdot13361=-66805\)
e: \(5+\left(-8\right)\cdot3\)
=5-24
=-19