1. The problem statement, all variables and given/known data Find the equation of the normal to the curve y=(6x+3)^(1/2) at the point for which x=13. 2. Relevant equations dy/dx=dy/du*du/dx y-y1=m(x-x1) 3. The attempt at a solution y=(6x+3)^(1/2) dy/dx=1/3(6x+3)^2 gradient of normal = -3(6x+3)^2 at x=13, dy/dx=-3(6x13+3)^2=19683. obviously a silly answer and the textbook disagrees. So at this point I could simplify y=(6x+3)^(1/2) to y=(2x+1)^2 maybe? Even after doing this, I end up with an even slightly smaller silly answer and the textbook still disagrees, unless the textbook is wrong, although this is highly unlikely. HELP!