1. The problem statement, all variables and given/known data Find an equation for the line perpendicular to the tangent to the curve y=x^3-4x+1 at the point (2,1). 2. Relevant equations point slope form, m * (-1/m) = -1 3. The attempt at a solution Derivate: y+3x^2-4 m=8 at x=2 Tangent line: y=8x-15 Answer: y=-x/8-15 Answer in book, y=-x/8 + 5/4 Where'd I go wrong?