Hard to understand what you are asking. You want something like u(x)=2x-5? You already have u_xx everywhere on the domain so the clause "or will I..." is hard to figure out.

Sir the soulution for u_xx is 2x-5 as u have pointed out. From the definition of Differential Quadrature method it gives the value of U_xx at one point like x=2. Instead of that Is it possible to get the solution in the form 2x-5 by differential quadrature method.

Since the DQ is somehow similar to Lagrange interpolation, I guess it might lead to something similar to Taylor expansion of U in the domain but with coefficients similar to a weighted average fashion.

Sir in DQ , what is the criterion to select the number of sampling points. What should be the number of sampling points that can give a good result?