`a, 3x (12x-4) -9x(4x-3)=30`
`<=> 36x^2 -12x - 36x^2 + 27x =30`
`<=> 15x =30`
`<=> x= 30/15`
`<=>x=2`
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`x^2 -4x+4=25`
`<=>(x-2)^2 =25`
`<=> (x-2)^2 = (+-5)^2`
\(\Leftrightarrow\left[{}\begin{matrix}x-2=5\\x-2=-5\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=7\\x=-3\end{matrix}\right.\)
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\(3\left(x+4\right)-x^2-8x-16=0\\ \Leftrightarrow3\left(x+4\right)-\left(x^2+8x+16\right)=0\\ \Leftrightarrow3\left(x+4\right)-\left(x+4\right)^2=0\\ \Leftrightarrow\left(x+4\right)\left(3-x-4\right)=0\\ \Leftrightarrow\left(x+4\right)\left(1-x\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x+4=0\\1-x=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=-4\\x=1\end{matrix}\right.\)
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\(\left(x-1\right)^2=\left(2x+14\right)^2\\ \Leftrightarrow\left(x-1\right)^2-\left(2x+14\right)^2=0\\ \Leftrightarrow\left[\left(x-1\right)-\left(2x+14\right)\right]\left[\left(x-1\right)+\left(2x+14\right)\right]=0\\ \Leftrightarrow\left(x-1-2x-14\right)\left(x-1+2x+14\right)=0\\ \Leftrightarrow\left(15-x\right)\left(3x+13\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}15-x=0\\3x+13=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=15\\3x=-13\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=15\\x=-\dfrac{13}{3}\end{matrix}\right.\)
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\(\left(5-2x\right)^3-27=0\\ \Leftrightarrow\left(5-2x\right)^3=27\\ \Leftrightarrow\left(5-2x\right)^3=3^3\\ \Leftrightarrow5-2x=3\\ \Leftrightarrow2x=2\\ \Leftrightarrow x=1\)
