What is the error in this implicit differentiation problem at the point (1,3)?

[hard_assteel]

[SOLVED] Implicit Differentiation

-4x^2+3xy+4y^3=-328

This is at the point (1,3)

Homework Equations

The Attempt at a Solution

here is my work

-4x^2+3xy+4y^3=-328
-8x+3xy'+3y+12y^2y'=0
-8x+3y=-3xy'-12y^2y'
-8x+3y=[-3x-12y^2]y'
y'=(-8x+3y)/(-3x-12y^2)
plug in x=1,y=3 then solve and get
m=-12/67
can you find the error?
It would be very much appreciated
thank you.

 

[cristo]

Try plugging in your values for x and y again.

 

[hard_assteel]

hey thankx, i accidently posted this question twice.