Based on the comments and the question i take it that you want to close the bottom area of the object and at the same time reduce the number of vertices to a minimum.
In that regard, i would do the following:
- Go in edit mode -> edge selection
- Select the edges that go along the long side ending at each side at the n-gon
- Press X and Delete the Edges
- Now switch to vertex selection
- Select the vertices at each side at the bottom edge of the n-gon, where the previously deleted edges were connected.
- Press X and Dissolve Vertices
- Now the left over edges can be used to create faces along the bottom area by selecting two edges and pressing F to fill the area between those.
All this sounds stretched and long, but once you know the steps it's done in a jiffy.