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-3(x-7)=-2x+9
\(\Leftrightarrow\) -3x-(-3).7=-2x+9
\(\Leftrightarrow\)-3x-(-21)=-2x+9
\(\Leftrightarrow\) (-3x)-(-2x)=9+(-21)
\(\Leftrightarrow\) -1x=(-12)
\(\Leftrightarrow\)-x=(-12)
Số đối của x là (-12) \(\Rightarrow\) x=12
vậy x=12
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A = -6 . ( -8 + 5 ) : 3 - 7 . ( -2 )
A = -6 . -3 : 3 - ( -14 )
A = 6 - ( -14 )
A = 20
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Ta có: A= 3+3\(^2\)+3\(^3\)+3\(^4\)+3\(^5\)+3\(^6\)+3\(^7\)+3\(^8\)+3\(^9\)+3\(^{10}\)
\(\Rightarrow\)A= (3+3\(^2\)) +(3\(^3\)+3\(^4\))+(3\(^5\)+3\(^6\)) +(3\(^7\)+3\(^8\))+(3\(^9\)+3\(^{10}\))
\(\Rightarrow\) A= 12 + 3\(^2\)(3\(^1\)+3\(^2\))+3\(^4\)(3\(^1\)+3\(^2\)) +3\(^6\)(3\(^1\)+3\(^2\)) + 3\(^8\)(3\(^1\)+3\(^2\))
\(\Rightarrow\) A= 12 + 3\(^2\). 12+3\(^4\) . 12+3\(^6\) .12+ 3\(^8\) .12
\(\Rightarrow\)A= 12 . ( 3\(^2\)+3\(^4\) +3\(^6\)+ 3\(^8\))
Vì 12 \(⋮\)4 \(\Rightarrow\)12 . ( 3\(^2\)+3\(^4\) +3\(^6\)+ 3\(^8\)) \(⋮\)4 hay A \(⋮\)4
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a/ \(2x^3=8x\)
\(2.8=2x^3\)
\(16=2x^3\)
\(x^3=16:2\)
\(x^3=8\)
\(x=2\)
phần b mk chưa nghiên cứu dc
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(-1)+3+(-5)+7+...+x=600
<=>[(-1)+3]+[(-5)+7]+....+[(-x)-2]+x]=600
Ta có 2+ 2 + .... + 2 = 600
=> 1 + 1 + .... + 1 = 300
Số dấu ngoặc [] là : \(\frac{x-3}{4}\)+ 1
=> \(\frac{x-3}{4}\)+ 1 = 300
=> \(\frac{x-3}{4}\)= 299
=> x - 3 = 299 . 4 = 1199
Vậy x = 1199
# Học Tốt
Tk cho mình nhé !
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\(\frac{\left|x-1\right|}{-8}=-\frac{3}{4}\)
=> |x - 1|.4 = (-8) . (-3)
=> |x - 1| . 4 = 24
=> |x - 1| = 24 : 4
=> |x - 1| = 6
=> \(\orbr{\begin{cases}x-1=6\\x-1=-6\end{cases}}\)
=> \(\orbr{\begin{cases}x=7\\x=-5\end{cases}}\)
Vậy ...
|2 - x| - 7 = 6/-2
=> |2 - x| = -3 + 7
=> |2 - x| = 4
=> \(\orbr{\begin{cases}2-x=4\\2-x=-4\end{cases}}\)
=> \(\orbr{\begin{cases}x=-2\\x=6\end{cases}}\)
vậy ...
\(\frac{-2}{1-x}=\frac{1-x}{-8}\)
=> (-2).(-8) = (1 - x).(1 - x)
=> (1 - x)2 = 16
=> (1 - x)2 = 42
=> \(\orbr{\begin{cases}1-x=4\\1-x=-4\end{cases}}\)
=> \(\orbr{\begin{cases}x=-3\\x=5\end{cases}}\)
Vậy ...
còn lại tự lm tương tự
\(\frac{6}{x-3}=\frac{9}{2x-7}\)
\(\Leftrightarrow9\left(x-3\right)=6\left(2x-7\right)\)
\(9x-27=12x-42\)
\(9x-27-12x+42=0\)
\(9x-12x-27+42=0\)
\(-3x+15=0\)
\(-3x=0-15\)
\(-3x=-15\)
\(x=\left(-15\right)\div\left(-3\right)\)
\(x=5\)
\(\frac{6}{x-3}=\frac{9}{2x-7}\left(đkxđ:x\ne3;\frac{7}{2}\right)\)
\(< =>6\left(2x-7\right)=9\left(x-3\right)\)
\(< =>12x-42=9x-27\)
\(< =>12x-9x=-27+42\)
\(< =>3x=15< =>x=\frac{15}{3}=5\)