Hey I am a first year student at the UofC and am having some trouble with a few calc problems. my proff is usless, she just gets mad when u ask her questions during her office hours. THe tutorials are also usless. The lectures even more so. These are the practice questions. I want to get solutions to them so I can do the assignment questions on my own. Thanks

Question #1

a.)If b=−3, find the x− coordinates of the points on the graph of f at which the tangent lines are horizontal. Enter the smaller answer first.

f(x)=(xe^x)/(3x+b)

b.)Find the value of b if the tangent line to the graph of f at the point (4f(4)) is horizontal.

Answer: The tangent line to the graph of f at the point (4f(4)) is horizontal exactly when b=?

Question #2

limx -> 0 x^2/ (cos 7 x - cos 4x)

Thanks alot