`a` , `5x(x-1)` `=` `x-1`
`⇒` `5x(x-1)` `-` `(x-1)` `=` `0`
`⇒` `(5x-1)` `(x-1)` `=` `0`
`⇒` \(\left[ \begin{array}{l}5x-1=0\\x-1=0\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}5x=1=>x=1/5\\x=1\end{array} \right.\)
`b` , `2(x+5)` `-` $x^{2}$ `-` `5x` `=` `0`
`⇒` `2(x+5)` `-` ($x^{2}$ `+` `5x`) `=` `0`
`⇒` `(2-x)` `(x+5)` `=` `0`
`⇒` \(\left[ \begin{array}{l}2-x=0\\x+5=0\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}x=2\\x=-5\end{array} \right.\)
