Einstein-Hilbert Action Derive from Christoffel Symbols and Quadratic Lagrangians?

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In Landau's bok "Classical Field Theory" pages: 372-373-374 they manage to get the Einstein-Hilbert action (after integrating by parts and use divergence theorem)

\mathcal L = \int dx^{4} \sqrt (-g) g^{ik}(\Gamma^{m}_{il}\Gamma^{l}_{km}-\Gamma^{l}_{ik}\Gamma^{m}_{lm})

from this and definition of 'Chrisstoffel symbols' the Lagrangian would be quadratic in the metric and its first derivatives , if we impose the constraint:

\mathcal{g}+1 =0 (does it has any physical meaning??)

and a Qadratic Lagrangian in the derivatives and fields can be evaluated by means of a Functional integral.
 
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Please clean up and edit. The last formula makes no sense.
 
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