1. The problem statement, all variables and given/known data A rower in a boat at a point P, 3km from the closest point Q on a straight shorline, wishes to reach a point r which is 5 km along the shoreline from Q. If he can row at 2km/h and walk at 4km/h along the shoreline, how far from point Q should the rower land the boat in order that the total time for the trip PR is minimized. 3. The attempt at a solution Okay so if I let x be the distance from point Q, then the equation should be: t = 2(x^2+9)^(1/2) + 4(5-x) right? Then dt/dx = 2x/(x^2+9)^(1/2) - 4 0 = 2x/(x^2+9)^(1/2) - 4 4(x^2+9)^(1/2) = 2x (x^2+9)^(1/2) = 1/2x x^2+9 = 1/4x^2 but that gives no solution. Could someone point me to where I went wrong please?