Need Help Please! Tangent Line Problems!! Hey, Okay, so here's the problem. I've got this quartic: 0 = -9x^4 + 190x^3 + 840x^2 + 1992x I need to find if this graph has two or more points with the same tangent line, and I'm at a loss. Given a point, I have no problem finding the tangent line (find slope with derivative, then just point/slope equation) but I don't know how to find two points on this graph with the same tangent line (if they exist). Please help! I'd also like to be able to do this for all graphs too, thanks!