I was practicing some basic math and I faced a question that I have no idea what does it requires me to do. Consider this simple function:
$$f(x) = x^2-5x-12$$
Part a and b where pretty easy. I tried to solve part C as you can see below. Unfortunately I cant imagine what has been asked in part D. What does coincident points of intersection mean? (Literally intersection means cutting each other and Coincident means on top of another AFAIK) Any help/explanation would be appreciated!
The point at which the line through $(1,-15)$ with slope $m$ cuts the graph of $f(n)$.
$$m=f'(n)=f'(1)=-1$$ $$y-y_1 = m(n-n_1)=>y+15=-1(n-1)$$ $$=>y=-n+1-15$$
The values of m such that the points of intersections found in $c$ are coincident.