If somebody has a lot to say about how to solve quadratic equations, it's reasonable to deduce that, relatively speaking, they are not knowledgeable about the subject. If they really knew about solving quadratic equations, then all they would need to say about it is the one fairly simple formula that you need to do it. There would be no need to discuss it at great length. At most they would need to prove the formula is correct, which wouldn't take more than a page.