function find_betas_approx_1 when dim(kernel(M))=4 in epnp.cpp

[fantasy567]

Thank you very much for open-source such a wonderful algorithm, the original article here said that when dim(kernel(M))=4 to calculate the beta needs to use Relinearization technology, and cpp code does not reflect this point. What I am puzzled about is why the beta1 obtained by solving L_(6*4)*Beta1(4,1)=Rho can be used as the initial value of the calculation coefficient beta, which can make the optimized solution converge to the closed solution? Look forward to your comments, Best wishes for you.(If there is a problem with grammar or expression, I hope you can understand~)