Please help me with Calculus. I need to know how to do these types of problems, but i was never exposed to them !! PLEASE HELP ME!

Question

snowsurf · Answer

Post the problem so we can take a look.

anonymous · Answer

Oh i attached a file of the problem up there

snowsurf · Answer

Part a.) You have right. 8x and 6y
part b.) So for your solution in part a you just plug in x=1 and y=2 into each derivative.
Part c.) dU(x,y) = 8xdx + 6ydy is the total differential because it include changes in both x and y and not just one variable as the partials you did in part a.
part d.) Set DU to 0. dU(x,y) = 8xdx + 6ydy

0 = 8xdx + 6ydy
-6ydy = 8xdx
$$\frac{ dy }{ dx } = -\frac{ 4x }{ 3y }$$

This is your solution for part d. So this says the change in dy/dx is based on the negative slope.

anonymous · Answer

Ahhh yes thank you! :D i did a-c correctly , but i still didn't know how to do the rest . thanks for reassuring me!! this is easy now.