\(1,5x^2-4\left(x^2-2x+1\right)+20=0\)
\(\Leftrightarrow5x^2-4x^2+8x-4+20=0\)
\(\Leftrightarrow x^2+8x+16=0\)
\(\Leftrightarrow\left(x+4\right)^2=0\)
\(\Rightarrow x+4=0\Rightarrow x=-4\)
\(2,x\left(x-2\right)-5x+10=0\)
\(\Leftrightarrow x\left(x-2\right)-5\left(x-2\right)=0\)
\(\Leftrightarrow\left(x-5\right)\left(x-2\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x-2=0\\x-5=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=2\\x=5\end{matrix}\right.\)
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