Understanding the Lagrangian Function for Maximization Problems

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The discussion revolves around understanding the Lagrangian function for a maximization problem in economics, specifically focusing on how to derive the first-order condition (FOC) with respect to r(y,α). The original poster expresses confusion regarding the notation and the process of differentiation, seeking clarity on applying Leibniz's rule and the chain rule. Respondents emphasize the need for more context and definitions of the notation used in the problem to facilitate understanding. A specific reference to a paper is provided to guide the discussion, particularly pointing to a problematic equation on page 14. The thread highlights the importance of clear communication and detailed explanations in complex mathematical discussions.
arfie
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Hi everyone!

I really need help for this. I have to read a paper in economics where some parts I don't understand.

Suppose:

S \equiv [\alpha,\bar{\alpha}]x[y,\bar{y}]
V^e(p_j,g_j,y+r(r\alpha)-T_j,\alpha)\equiv \underset{h}{\text{max}}U(y+r(r,\alpha)-T_j,p_jh,h,g_j;\alpha)

And then from maximization problem I have a Lagrangian function as follows:

L=<br /> \sum_{i = 1}^{J} \Big[\int_S \omega (y,\alpha) V^e(p_i,y+r(y,\alpha)-T_i,g_i,\alpha) a_i(y,\alpha)f(y,\alpha)\,dy\,d\alpha<br /> + \omega_R(R/J+\int_0^{p_i/(1+t_i)}H^i_s(z)\,dz)\Big]

\lambda_1[R+\int_S r(y,\alpha)f(y,\alpha)\,dy\,d\alpha]+\lambda_2[\int_S h_d(p_i,y+r(y,\alpha)-T_i,g_i,\alpha)a_i(y,\alpha)f(y,\alpha)\,dy\,d \alpha-H_S^i]

How can I solve for FOC for the lagrangian function with respect to r(y,\alpha)? What rules should I use? I guess it has something to do with Leibniz's rule and chain rule but I'm not sure. Thanks!
 
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Definitely not enough info here for anyone to understand what's going on. For instance, "solve for FOC for the lagrangian function with respect to r(y,a)" is meaningless to me.
 
joeblow said:
Definitely not enough info here for anyone to understand what's going on. For instance, "solve for FOC for the lagrangian function with respect to r(y,a)" is meaningless to me.

Thanks for the reply.
I mean "how to get first derivative of L w.r.t r(y,a) which is dL/dr(y,a)?"
 
arfie said:
Thanks for the reply.
I mean "how to get first derivative of L w.r.t r(y,a) which is dL/dr(y,a)?"

Sorry, but you're going to have to give way more information. Start by defining all the notation you use. Describe the actual problem that's given. Maybe give a reference to where you have seen this.
 
micromass said:
Sorry, but you're going to have to give way more information. Start by defining all the notation you use. Describe the actual problem that's given. Maybe give a reference to where you have seen this.

Sorry if it's not that clear. The reference is here: http://www.nber.org/papers/w17251.pdf
My problem is in page 14, equation (20). I don't know how to get it.
 

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