Find the slope of the tangent line of the parabola 2x - x^2 at point (2,0):

So I have to use the forumla

m = lim f(a + h) - f(a) / h

h->0

So we have to find f(a) which = 0.

Then put in that to f(a + h) which = 2(0 + h) - (0+h)^2

So then you get for the equation:

(2h - 0) / h

Which would then equal 2, but the answer is -2...can anyone help?