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a)\(\left(x+8\right)-11=20-15\)
\(\left(x+8\right)-11=5\)
\( x+8=5+11\)
\(x+8=16\)
\(x=8\)
b) \(2x-\left(3+x\right)=5-7\)
\(2x-\left(3+x\right)=-2\)
\(2x-3-x=-2\)
\(x=1\)
c) \( \left(3x-2^4\right)\times7^5=2\times7^6\)
\(3x-2^4=2\times\left(7^6:7^5\right) \)
\(\left(3x-2^4\right)=2\times7^2\)
\(3x-2^4=2\times49\)
\(3x-16=98\)
\(3x=114\)
\(x=38\)
Bài làm
a) Ta có: x( x + 7 ) = 0
\(\Rightarrow\orbr{\begin{cases}x=0\\x+7=0\end{cases}\Rightarrow\orbr{\begin{cases}x=0\\x=-7\end{cases}}}\)
Vậy x = { 0; -7 }
b) Ta có: ( x + 12 )( x - 3 ) = 0
\(\Rightarrow\orbr{\begin{cases}x+12=0\\x-3=0\end{cases}\Rightarrow\orbr{\begin{cases}x=-12\\x=3\end{cases}}}\)
Vậy x = { -12; 3 }
c) \(\frac{2}{x}=\frac{-8}{12}\)
\(\Rightarrow x.\left(-8\right)=2.12\)
\(\Rightarrow x.\left(-8\right)=24\)
\(\Rightarrow x=24:\left(-8\right)=-3\)
Vậy x = -3
a, x(x+7)=0 b,(x+12).(x-3)=0 c,2/x= -8/12
x+7=0.x x+12=0 hoặc x-3=0 2/x= -2/3
x+7=0 x=0-12 hoặc x=0+3 2/x= 2/-3
x=0 x=-12 hoặc x=3 =>x=-3
\(a,-\frac{9}{12}=-\frac{9:3}{12:3}=-\frac{3}{4}\)
\(\frac{-18}{-24}=\frac{\left(-18\right):\left(-6\right)}{\left(-24\right):\left(-6\right)}=\frac{3}{4}\)
\(-\frac{35}{70}=-\frac{35:35}{70:35}=\frac{1}{2}\)
\(-\frac{9}{27}=-\frac{9:9}{27:9}=-\frac{1}{3}\)
\(b,\frac{1313}{4242}=\frac{1313:101}{4242:101}=\frac{13}{42}\)
\(\frac{-353535}{-424242}=\frac{\left(-353535\right):\left(-70707\right)}{\left(-424242\right):\left(-70707\right)}=\frac{5}{6}\)
\(c,\frac{2^3\times4^3\times5^4}{8^2\times25^3\times7}=\frac{2^3\times4^3\times25^2}{8\times8^2\times25^2\times25\times7}\) ( 4^3 = 8^2 ; 5^4 = 25^2 )
\(=\frac{1}{25\times7}=\frac{1}{175}\)
\(a.\frac{-9}{-12}=\frac{-9:3}{-12:3}=\frac{-3}{-4}.\)
\(\frac{-18}{-24}=\frac{-18:6}{-24:6}=\frac{-3}{-4}\)
\(\frac{-35}{-70}=\frac{-35:35}{-70:35}=\frac{-1}{-2}\)
\(\frac{-9}{-27}=\frac{-9:9}{-27:9}=\frac{-1}{-3}\)
a) -45 -( - x - 3) - 12 = -15
=> -45 + x + 3 - 12 + 15 = 0
=> x - 39 = 0
=> x = 39
b) -32 -(-3 + 7) - x = 7 + (-2-8)
=> -32 + 3 - 7 - x = 7 - 2 - 8
=> -32 + 3 - 7 - 7 + 2 + 8 = x
=> x = -33
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