giúp hộ vs

bài 3.
a, 
$ \begin{array}{l}
5x(x-1)=x-1\\
5x^{2} -5x\ =\ x-1\\
5x^{2} -6x+1=0\\
5x^{2} -5x+1-x=0\\
5x( x-1) -( x-1) =0\\
( x-1)( 5x-1) =0\\
\rightarrow \left[ \begin{array}{l l}
x\ =\ 1 & \\
x\ =\ \frac{1}{5} & 
\end{array} \right.
\end{array}$
b,
$ \begin{array}{l}
(x-3)^{2} -x^{2} =4x-1\\
( x-3-x)( x-3+x) =4x-1\\
-3( 2x-3) =4x-1\\
-6x\ +\ 9\ =4x\ -\ 1\\
-10x\ =\ -10\\
x\ =\ 1
\end{array}$