Question 1126203

Complete the general form equation of the parabola that passes through 
(2,−21)with vertex at (−1,−3)

Enter the quadratic expression in general form, 
ax^2+bx+c.
<pre>Vertex from: {{{matrix(1,3, y, "=", a(x - h)^2 + k)}}}
{{{matrix(1,3, - 21, "=", a(2 - - 1)^2 - 3)}}} ------- Substituting (2, - 21) for (x, y) and (- 1, - 3) for (h, k) 
- 21 = 9a - 3
- 21 + 3 = 9a
- 18 = 9a
{{{matrix(1,5, a, "=", (- 18)/9, "=", - 2)}}}
{{{matrix(1,3, y, "=", - 2(x + 1)^2 - 3)}}} ------- Substituting - 2 for a, and (- 1, - 3) for (h, k) 
{{{matrix(1,3, y, "=", - 2(x^2 + 2x + 1) - 3)}}}
{{{highlight_green(matrix(1,5, y, "=", - 2x^2 - 4x - 2 - 3, "or", - 2x^2 - 4x - 5))}}}