Abstract
In this talk, we study the solvability of the simplest elliptic equations. 
More precisely, the input data is given in L_2 space and firstly we get L_2 estimate.
We prove certain type of maximum principle in the next step and combining above two results, we can get a solution for the simplest equations. Furthermore, by using the idea to get a solution, we can derive a solution space, Sobolev space, naturally.