Question 992106
Either of these, maybe both, should be great help:


<a href="https://www.youtube.com/watch?v=M8LGsQMwwj4">Equation of a parabola, derivation</a>


<a href="https://www.youtube.com/watch?v=Wworlx39KfQ">Equation of parabola derivation for vertex not at origin</a>