Here I am supposed to show that the equation of the right is a solution of the differential equation on the left. I have solved a few problems of this type already but I have trouble with this one. Did I make a mistake and overlooked something somewhere or the condition 'for x>0' sort of means that it is okay even if the other side of the equation turns out to be negative? In the book's answer key it says that for this problem the equation on the right is a solution of the DE