Its true, because it is a linear combination of the two solutions (i.e. linear operator). The solution space, I believe is a vector space, and the linear combination of two solutions has to be in the vector space by definition.
Its true, because it is a linear combination of the two solutions (i.e. linear operator). The solution space, I believe is a vector space, and the linear combination of two solutions has to be in the vector space by definition.