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bài 1
a) \(15+\left(32-2x\right)=65\)
\(32-2x=65-15\)
\(32-2x=50\)
\(2x=32-50\)
\(2x=-18\)
\(x=-18:2\)
\(x=-9\)
vậy \(x=-9\)
b)\(18.\left(x-5\right)^2=72\)
\(\left(x-5\right)^2=72:18\)
\(\left(x-5\right)^2=4=2^2\)
\(x-5=2\)
\(x=2+5=7\)
vậy \(x=7\)
c)\(\left|19-x\right|-6=0\)
\(\left|19-x\right|=0+6=6\)
\(19-x=\pm6\)
\(\left[{}\begin{matrix}19-x=6\\19-x=-6\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=13\\x=25\end{matrix}\right.\)
vậy \(x\in\left\{13;25\right\}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
bài 1 :
-72.(15-49)+15.(-56+72)
= -72.(-34) + 15.16
= 2448 + 240
= 2688
bài 2 :
-2x-8=-72
=> -2x = -72 + 8
=> -2x = -64
=> x = -64 : (-2)
=> x = 32 thuộc Z
vậy____
Bài 1:
-72 . ( 15 - 49 ) + 15 . ( -56 + 72 )
= -72 . ( -34 ) + 15 . 16
= 2448 + 240
= 2688
Bài 2:
-2x - 8 = -72
-2x = -72 + 8
-2x = -64
x = ( -64 ) : ( -2 )
x = 32
![](https://rs.olm.vn/images/avt/0.png?1311)
2x2 - 72 = 0
2x2 = 0 + 72
2x2 = 72
x2 = 72 : 2
x2 = 36
x2 = 62 = ( - 6 )2
=> \(\orbr{\begin{cases}x=6\\x=-6\end{cases}}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(2x^2-72=0\)
\(\Rightarrow2x^2=0+72\)
\(\Rightarrow2x^2=72\)
\(\Rightarrow x^2=72:2\)
\(\Rightarrow x^2=36\)
\(\Leftrightarrow x=6\)
2x2-72=0
<=> 2x2=0+72
<=> 2x2=72
<=> x2=72/2
<=> x2=36
<=> x=6 hoặc x=-6
Vậy x=6 hoặc x=-6
![](https://rs.olm.vn/images/avt/0.png?1311)
\(72^{45}-72^{44}=72^{44}.\left(72-1\right)=72^{44}.71\)
\(72^{44}-72^{43}=72^{43}.\left(72-1\right)=72^{43}.71\)
Vì \(72^{44}>72^{43}\Rightarrow72^{45}-72^{44}>72^{44}-72^{43}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
72-(33+x)=26
33+x=72-26
33+x=46
x=46-33
x=13
k với đang thiếu điểm nè
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b: \(\left(2x+1\right)^2=25\)
=>\(\left[{}\begin{matrix}2x+1=5\\2x+1=-5\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}2x=4\\2x=-6\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-3\end{matrix}\right.\)
c: \(\left(1-3x\right)^3=64\)
=>\(\left(1-3x\right)^3=4^3\)
=>1-3x=4
=>3x=1-4=-3
=>x=-3/3=-1
d: \(\left(4-x\right)^3=-27\)
=>\(\left(4-x\right)^3=\left(-3\right)^3\)
=>4-x=-3
=>x=4+3=7
e: \(x^2-5x=0\)
=>\(x\left(x-5\right)=0\)
=>\(\left[{}\begin{matrix}x=0\\x-5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=5\end{matrix}\right.\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,\Rightarrow x+2=-40\\ \Rightarrow x=-42\\ b,\Rightarrow6x-7-2x=5\\ \Rightarrow4x=12\Rightarrow x=3\\ c,\Rightarrow68-56-x=-2\\ \Rightarrow12-x=-2\\ \Rightarrow x=14\)