Calculus of a Single Variable, Chapter 2, 2.1, Section 2.1, Problem 8

The given function is:-
f(x) = 5 - (x^2)
differentiating both sides w.r.t 'x' we get
f'(x) = 0 - 2x
Now, slope of the tangent at the point (3,-4) = f'(3) = - 2*3 = -6