1. The problem statement, all variables and given/known data A spaceship moves along y = x3 - 8x in the positive x-direction. Shutting off the engines at P allows it to move off along the tangent at P. Find P so that the ship can reach the point (4,0). 2. Relevant equations Dunno 3. The attempt at a solution So I start with P = (x1,y1). The slope of the tangent is then m = 3x12 - 8 from the first derivative. Then I need P, so I went like this: m = (y2 - y1) / (x2 - x1) = 3x12 - 8 where y2 and x2 are (4,0). But now I have 1 Eqn. and 2 variables so I can't solve. I was thinking of using y = mx + b because I have y and x, plus an equation for m but then I end up with 2 equations and 3 variables because of the b term. Please help!