`text{ Bài 2: Tìm x}`
`a)` `(2x-1)(x+1)-x(2x+3)+1=0`
`⇔2x^2+2x-x-1-2x^2-3x+1=0`
`⇔-2x=0`
`⇔x=0`
`text{ Vậy x = 0}`
`b)` `x(x-1)=2`
`⇔x^2-x=2`
`⇔x^2-x-2=0`
`⇔x^2+x-2x-2=0`
`⇔x(x+1)-2(x+1)=0`
`⇔(x+1)(x-2)=0`
`⇔` \(\left[ \begin{array}{l}x+1=0\\x-2=0\end{array} \right.\) `⇔` \(\left[ \begin{array}{l}x=-1\\x=2\end{array} \right.\)
`text{ Vậy ∈ { - 1 ; 2}}`
