`a) (x - 2)^2 - x.(x - 1) = 9`

`<=> x^2 - 4x + 4 - x^2 + x = 9`

`<=> -3x = 5`

`<=> x = -5/3`

Vậy `x = -5/3`

`b) (x + 1)(x^2 - x + 1) - x^3 + 2x = -35`

`<=> x^3 + 1 - x^3 + 2x = -35`

`<=> 2x = -36`

`<=> x = -18`

Vậy `x = -18`

`c) x^2 - 4x - 5 = 0`

`<=> x^2 - x + 5x - 5 = 0`

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

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

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

`<=>`$\left[\begin{matrix} x-1=0\\ x+5=0\end{matrix}\right.$

`<=>`$\left[\begin{matrix} x=1\\ x=-5\end{matrix}\right.$

Vậy `x\in{1; -5}`

`d) (5x + 8)^2 - (3x + 2)^2 = 0`

`<=> (5x + 8 - 3x - 2)(5x + 8 + 3x + 2) = 0`

`<=> (2x + 6)(8x + 10) = 0`

`<=>`$\left[\begin{matrix} 2x+6=0\\ 8x+10=0\end{matrix}\right.$

`<=>`$\left[\begin{matrix} 2x=-6\\ 8x=-10\end{matrix}\right.$

`<=>`$\left[\begin{matrix} x=-3\\ x=\frac{-5}{4}\end{matrix}\right.$

Vậy `x\in{-3; \frac{-5}{4}}`