Calculus of Variations - please help?

I have answered the question: Find the extremals of the function: J[y]=integral from 0 to 1 of (-(y')^2 + y)) dx and found the extremal y = (-1/4)x^2 + (5/4)x which I think is correct. I have now been asked to find whether it is a maximum or a minimum but I don't understand how to. Please help!