1: \(\Leftrightarrow\left\{{}\begin{matrix}x< =8\\x^2-16x+64=x^2-3x-1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x< =8\\-13x=-65\end{matrix}\right.\Leftrightarrow x=5\)
2: \(\dfrac{x}{1-x}+3=\dfrac{x+5}{2x+3}\)
\(\Leftrightarrow x\left(2x+3\right)+3\left(1-x\right)\left(2x+3\right)=\left(x+5\right)\left(1-x\right)\)
\(\Leftrightarrow2x^2+3x+3\left(2x+3-2x^2-3x\right)=x-x^2+5-5x\)
\(\Leftrightarrow2x^2+3x+6x+9-6x^2-9x=-x^2-4x+5\)
\(\Leftrightarrow-4x^2+9+x^2+4x-5=0\)
=>-3x^2+4x+4=0
hay \(x\in\left\{2;-\dfrac{2}{3}\right\}\)
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