Line Tangent to a Curve at a Point. PART 1. f(a + h) - f(a) Using the definition of derivative of a function at a point, f'(a) = lim ' find the slope of the tangent to the curve at the given point. h0 h f(x)=-10x+12x+11; a=-3 The slope of the tangent to the curve at a = -3 is Note: Enter a numerical value for the slope.