Find the slope of the tangent to the parabola y=-3x^2 + 4x - 7 when x=a. I know how to get the limit using the tangent so i end up with a slope in terms of a (you can also get it using the derivative) but now the next part states: At what point on the parabola is the tangent perpendicular to the line 3x - 4y + 8=0 and all that i get from that question is that the tangent for the point on the parabola will have a slope of -4/3 (negative reciprocal)
so you have the derivative in terms of a, right? Let's call it D(a). You're looking for the value for a such that this expression is equal to -4/3. So what about solving D(a)=-4/3 for a ..?