The parabola is wider than it's parent function, y = x^2. Therefore the coefficient, of x^2 (when you refer to quadratic equations it's a) should be greater than 1. Let's take 2.
y = 2x^2
Now it is reflected across the x-axis, so the equation turns to y = -2x^2. The vertex is shifted down 4. Note that it is shifted down, along the y-axis. This makes 'c' (again quadratic equations) -4.
