1. The problem statement, all variables and given/known data Show that a solution to y' = y(6-y) has a turning point when y = 3. 3. The attempt at a solution If y has a turning point, then y'' = 0. I find that y'' = 6 - 2y. If i solve 0=6-2y i get y =3. But how do i know that this is a turning point? yes, y'' equals zero, but don't i have to know that y'' changes sign when 'passing' zero? It could be that the solution is for instance concave, then linear, then concave again as x increases? When the function/solution is linear, the y'' is zero, right?