What is 400x800 do any one knows

If the ratio of sum of the first m and n terms of an ap is m2 : n2 , show that the ratio of its mth and nth terms is (2m − 1) : (2n − 1).

F(x) = 1/x g(x)=x-4 can you evaluate (g*f)(0) ? why or why not?

Use complete sentences to differentiate between a regular tessellation, and a pure tessellation. be sure to include specific types of polygons in your explanation.