Bit of help please chaps:

Finding the vertex of a Parabola, two methods, graph and formula.

Formula:

Now when i've graphed it, it comes out positive in terms of co-ordinates, however when you apply the formula:

Letting a= -5, b= 10, c= 0

For X Co-Ord

For Y Co-Ord

The vertex of the parabola on the graph shows X = 1 and Y = 5 so how or why am i getting the negatives?!

Thanks