why using $\frac{-b\pm\sqrt{b^2-4ac}}{2a}$ to factorize a polynomial degree 2 dose not always work i tried to factorize $5x^3-11x^2+2x$ so i took out $x$ and used $\frac{-b\pm\sqrt{b^2-4ac}}{2a}$ to find the roots 2 and $\frac{1}{5}$ but to my surprise multiplying the roots like so $x(x-2)\cdot(x-\frac{1}{5})$ produces a fifth of the original polynomial what did i do wrong?

What you did would be right if your polynomial was monic, which means if its leading coefficient was $1$. But the truth is its leading coefficient is $5$. So what you have to do is take out $\frac{1}{5}x$ instead of just taking out $x$, and then find the roots. 
