[tex] 2x^{2} - x - 1[/tex]
Δ = 1 + 8 = 9 => [tex] x_{1} = \frac{1+3}{4} = 1 [/tex]
[tex] x_{2} = \frac{1-3}{4} = \frac{-2}{4} = - \frac{1}{2} [/tex]
[tex]2 x^{2} - x - 1 = 2 ( x - x_{1} ) ( x - x_{2} ) = 2 ( x - 1) ( x + \frac{1}{2} ) = ( x - 1 ) ( 2x +1 )[/tex]
