a: =>2(x+3)=4(x+1)
=>x+3=2(x+1)
=>2x+2=x+3
=>x=1
b: \(\Leftrightarrow\left\{{}\begin{matrix}x>=\dfrac{5}{2}\\\left(2x-5-x+1\right)\left(2x-5+x-1\right)=0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x>=\dfrac{5}{2}\\\left(x-4\right)\left(3x-6\right)=0\end{matrix}\right.\Leftrightarrow x=4\)
c: \(\Leftrightarrow\left(x-3\right)^6\left[\left(x-3\right)^4-1\right]=0\)
=>(x-3)(x-4)(x-2)=0
hay \(x\in\left\{3;4;2\right\}\)