Re: "I don't understand the Quadratic / Cubic Formula."
[S2 - A Level Mathematics: Functions & Graphs] (Long Video. If you feel like you don't understand graphs, this is worth a watch)
You might be used to the Quadratic Formula if you're familiar with the Secondary School Maths curriculum. It's a very simple equation that spits out the answers you want as long as you put the coefficients in the right parts of the equation.
It's also one of the first times you were given a mathematical formula featuring such complex algebraic arrangements & for most of you, realise how useful algebra is - Just find out what those numbers before your x^2 and x are, pop them in and you'll get the answer 'magically'.
There is a more complex iteration known as the cubic formula, which isn't taught early on in the curriculum that is also really useful for solving cubic equations. This video will give you a thorough understanding of the formula's machinations and how every part of the equation contributes to the graph in a meaningful way.