Here's the question you clicked on:
justinyum
In the problems given for the Constrained Differentials section 42 of the course, I am having difficulty understanding the solution to problem 3. It appears that in wx and wy, z is set to zero for some strange reason despite no further manipulation of wz. Is there a reason for this or is it simply a mistake? As a note, earlier in the problem a negative sign was neglected in moving (2xy+y^2)dx to the other side of the equation of when taking the differentials of the constraint equation, which would invalidate the solution as given anyway.