The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= 4.6056\\[1 em]x_2 &= -2.6056 \end{aligned} $$Step 1:
Get rid of fractions by multipling equation by $ \color{blue}{ 2 } $.
$$ \begin{aligned} -\frac{1}{2}x^2+x+6 & = 0 ~~~ / \cdot \color{blue}{ 2 } \\[1 em] -x^2+2x+12 & = 0 \end{aligned} $$Step 2:
The solutions of $ -x^2+2x+12 = 0 $ are: $ x = 1-\sqrt{ 13 } ~ \text{and} ~ x = 1+\sqrt{ 13 }$.
You can use step-by-step quadratic equation solver to see a detailed explanation on how to solve this quadratic equation.