Studying quadratic equations and i'm at a chapter where it details the sum and product of the roots of a quadratic.

It starts off with the following:

If $\displaystyle \alpha$ and $\displaystyle \beta$ are the roots of the quadratic equation $\displaystyle ax^2+bx+c=0$ then $\displaystyle (x-\alpha)(x-\beta)=0$

Can anyone explain how that equality conclusion is reached?