Tìm x, biết: a. 5x(x – 1) = x – 1 b. 2(x + 5) – x2 – 5x = 0

`a. 5x(x – 1) = x – 1`

`<=>(x-1)(5x-1)=0`

`=>`\(\left[ \begin{array}{l}x-1=0\\5x-1=0\end{array} \right.\)

`=>`\(\left[ \begin{array}{l}x=1\\x=\dfrac{1}{5}\end{array} \right.\)

`b. 2(x + 5) – x^2 – 5x = 0`

`<=>2(x+5)-x(x+5)=0`

`<=>(x+5)(2-x)=0`

`=>`\(\left[ \begin{array}{l}x+5=0\\2-x=0\end{array} \right.\)

`=>`\(\left[ \begin{array}{l}x=-5\\x=2\end{array} \right.\)