Total Differentiation of implicitly defined function with many variables
I need help sorting out some basic calculus. I need to take the total derivate of the following function with respect to the variable
. Note, the variables are y and
where
goes from 1 to 7, while all other symbols are constants:
I want to calculate the total derivative of
with respect to the variable 
Where
satisfy the following set of equation seven equations in eight variables
and
. Assuming these equations have a solution and it is unique, what is happening is that I get to choose
and for every choice of
we get some values for
. The total derivative I need to calculate is the first order condition I need to figure out an optimal choice of
. It is easy to verify in the context of the problem that my solution is not a boundary solution. So anyway,
satisfy the following set of equation seven equations in eight variables
and
. :







This is how I have solved this:
Need to compute:

I will take the total derivative of the constraints to solve for
,
, 
So, we get the following equations:

 + k_2 (\frac{d x_3}{dy}x_6^{k_1}+ x_3 k_2 x_6^{k_2-1} \frac{d x_6}{d y})&=&0\\)

 + k_2 (\frac{d x_3}{dy}x_7^{k_1}+ x_3 k_2 x_7^{k_2-1} \frac{d x_7}{d y})&=&0\\)


These equations are linear in
,
,
. I can solve for them and plug back into ($\ref{eq:main}$) to get the final answer.
Is this correct? or am I doing something wrong? If this is correct, I'd appreciate it if you can recommend some reading I could read which covers implicit differentiation in more than two variables so I can understand how to think about this without having doubts. If this is incorrect, then could you please tell me why and then again recommend some place I can read about this. Thanks