Question 1189918

The graph of a certain quadratic y = ax^2 + bx + c is a parabola with vertex (-4,0) which passes through the point (1,-75). What is the value of a?
<pre>That's ABSOLUTELY unnecessary to complete the square and go through all that "mumbo-jumbo" as the other person did.
This is done as easily as: Vertex form of the equation 
                            of a parabola: {{{matrix(1,3, y, "=", a(x - h)^2 + k)}}}
                                        {{{matrix(1,3, - 75, "=", a(1 - - 4)^2 + 0)}}} ------ Substituting (1, - 75) for (x, y) and (- 4, 0) for (h, k)
                                         - 75 = 25a
                                       {{{highlight_green(matrix(2,3, (- 75)/25, "=", a, - 3, "=", a))}}}
                                       That's ALL!!</pre>