The land of the house is square, but the back of the house is triangular. Is it good from the perspective of feng shui?

Generally speaking, triangular land is bad feng shui, that is to say, houses are built on triangular terrain. In this case, there will generally be a road rush or scissors difference, which is not good for the house itself.

But in your case, a piece of land behind the house is triangular, which means there is no problem in front of the house. If the triangular land behind it does not form a scissors-shaped intersection, there is no problem.