`1.`
`2(x + 2) + x + 1 = 0`
`<=> 3x = -5`
`<=> x = -5 : 3`
`<=> x = -5/3`
`Vậy: x = -5/3`
`2.`
`x(x - 1) + x - 1 = 0`
`<=> (x - 1)(x + 1) = 0`
`=>` \(\left[ \begin{array}{l}x - 1 = 0\\x + 1 = 0\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x = 0 + 1\\x = 0 - 1\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x = 1\\x = -1\end{array} \right.\)
`Vậy: x ∈ {1; -1}`
`3.`
`2x(x - 2) + 2x - 4 = 0`
`<=> 2x( x- 2) + 2(x - 2) = 0`
`<=> (x - 2)(2x + 2) = 0`
`=>` \(\left[ \begin{array}{l}x - 2 = 0\\2x + 2 = 0\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x = 0 + 2\\2x = 0 - 2\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x = 2\\2x = -2\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x = 2\\x = -2 : 2\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x = 2\\x = -1\end{array} \right.\)
`Vậy: x ∈ {2; -1}`
`4.`
`3(x + 1) - x- 1 = 0`
`<=> 3(x + 1) - (x + 1) = 0`
`<=> (x + 1)(3 - 1) = 0`
`<=> x + 1 = 0`
`<=> x = 0 - 1`
`<=> x = -1`
`Vậy: x = -1`
`5.`
`3x(2x - 1) - 2x + 1 = 0`
`<=> 3x(2x - 1) - (2x - 1) = 0`
`<=> (2x - 1)(3x - 1)=0`
`=>` \(\left[ \begin{array}{l}2x - 1 = 0\\3x - 1 = 0\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}2x = 0 + 1\\3x = 0 + 1\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}2x = 1\\3x = 1\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x = 1 : 1\\x = 1 : 3\end{array} \right.\)
`=>` $\left[\begin{matrix} x = \dfrac{1}{2}\\ x = \dfrac{1}{3}\end{matrix}\right.$
`Vậy: x ∈ {1/2; 1/3}`
`6.`
`2x(x - 5) - 3x + 15 = 0`
`<=> 2x^2 - 10x - 3x + 15 = 0`
`<=> 2x^2 - (10x + 3x) + 15 = 0`
`<=> 2x^2 - 13x + 15 = 0`
`<=> (2x^2 - 10) - (3x - 15) = 0`
`<=> 2x(x - 5) - 3(x - 5) = 0`
`<=> (x - 5)(2x - 3) = 0`
`=>` \(\left[ \begin{array}{l}x - 5 = 0\\2x - 3 = 0\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x = 0 + 5\\2x = 0 + 3\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x = 5\\2x = 3\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x = 5\\x = 3 : 2\end{array} \right.\)
`=>` $\left[\begin{matrix} x = 5\\ x = \dfrac{3}{2}\end{matrix}\right.$
`Vậy: x ∈ {5; 3/2}`
