A. `-b/(2a)` gives the x-coordinate of the vertex of the parabola if `y=ax^2+bx+c`
B. `y=x^2` is the prototypical parabola -- it is the base function you normally consider when looking at transformations. (The parent function.)
C. `b^2-4ac` is the discriminant -- the sign of the discriminant tells you how many solutions and of what type there are for a quadratic equation.
D. `y=a(x-h)^2+k` is the vertex form of a quadratic -- the vertex is at (h,k)
E. `x=(-b+-sqrt(b^2-4ac))/(2a)` is the quadratic formula -- if `y=ax^2+bx+c` then the formula gives the solutions.