`(x-2)^2 -3x +6 =0`
`<=> (x-2)^2 - 3(x-2) =0`
`<=> (x-2)(x-2-3)=0`
`<=> (x-2)(x-5) =0`
`<=>[(x=2),(x=5):}`
`9x^2 - (x-4)^2 =0`
`<=>(3x-x+4)(3x+x-4) =0`
`<=>(2x+4)(4x-4) =0`
`<=> [(2x=-4),(4x=4):}`
`<=> [(x=-4/2=-2),(x=4/4=1):}`
\(a,\left(x-2\right)^2-3\left(x-2\right)=0\\ \Rightarrow\left(x-2\right)\left(x-2-3\right)=0\\ \Rightarrow\left(x-2\right)\left(x-5\right)=0\\\Rightarrow\left[{}\begin{matrix}x-2=0\\x-5=0\end{matrix}\right. =>\left[{}\begin{matrix}x=2\\x=5\end{matrix}\right.\\ ----------\\ b,9x^2-\left(x-4\right)^2=0\\ \Rightarrow\left(3x-x+4\right)\left(3x+x-4\right)=0\\ \Rightarrow\left(2x+4\right)\left(4x-4\right)=0\\ \Rightarrow\left[{}\begin{matrix}2x+4=0\\4x-4=0\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=-2\\x=1\end{matrix}\right.\)