Question

please help?
Consider the function z=x^7y +28x^6 -16384y. Find and classify all critical points of the function?

the critical point with the smallest x-coordinate is?
all i know is the point is a saddle point!

Answer 1

Take the derivative of the function z. Then set the derivative function equal to zero and solve for values of x. The take the smallest x value you get and plug it into the original function z. You will then have the "smallest x coordinate".

Answer 2

the point i got was -24,1 ? but it says its wrong! i think im doing the derivative wrong?

Answer 3

is it partial derivative? are you in cal3?

Answer 4

im not sure to be honest

Answer 5

to me, it sounds like partial derivative, but I am trying, it is not as easy as riuy said.

Answer 6

when i tried to get the derivative i got this 7 x^5 (24+x y)?

Answer 7

it could be the partial deriviative so :)

Answer 8

ok, so, you have x =0 or xy =-24?

Answer 9

i got the x to be -24 and y to be 1 but it wasnt right?

Answer 10

how can you get that? you cannot arbitrarily set y =1 to get that

Answer 11

i duno i just threw figures around on wolfram?

Answer 12

think more. sorry , I'll be back later. emergency situation, tolerate, sorry again

Answer 13

your ok :) thanks for the help

Answer 14

i got it the points were 4,-6 :)

Answer 15

I'm back. hey, friend, if you don't know, you are let it go and accept no credit. use the math tool without understanding means you suicide.

Answer 16

i got the points with wolfram and then the smallest x value was 4 and the point with 4 was (4,-6), subbed it in and was right and its a sadde point :)

Answer 17

ok, as long as you understand, you are good. good luck

Answer 18

ya i do :) could you help me with my other question? im stuck on trying to get fxx!

Answer 19

partial derivative? if it is so, I think I can help. ok, post it

Answer 20

ya it is :) http://openstudy.com/study#/updates/51561557e4b0507ceba19405