1. ## MATH 251 problems,

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

2. For starters, please stop whining and blaming the entire planet. If you're sttruggling, it doesn't ahve to be anyone's fault. Why not just come on over here and see if we can help a little? It's lots easier than beating up everyone and everything at UofC.

a) Can you find the first derivative of f(x)? That is what you will need. There are Product Rules and Quotient Rules in there. It is a little tedous, but you can do it. Finally, find 'x' where the Numerator is zero (0), and make sure the Denominator doesn't vanish there as well. That's about it.

b) Can you find the first derivative of f(x)? That is what you will need. There are Product Rules and Quotient Rules in there. It is a little tedous, but you can do it. Finally, find 'b' where the Numerator is zero (0), and make sure the Denominator doesn't vanish there as well. That's about it.