On the classifying problem for the class of real solvable Lie algebras having 2-dimensional or 2-codimensional derived ideal

Let $\mathrm{L}\mathrm{i}\mathrm{e}(n,k)$ denote the class of all $n$-dimensional real solvable Lie algebras having $k$-dimensional derived ideal ($1 \leqslant k \leqslant n-1$)\mathrm{.}In1993,theclass$$\mathrm{L}\mathrm{i}\mathrm{e}$ \left(n, 1\right)$ was completely classified by Sch"obel \cite{Sch93}. In 2016, Vu A. Le et al. \cite{VHTHT16} considered the class $\mathrm{L}\mathrm{i}\mathrm{e}(n,n-1)$ and classified its subclass containing all the algebras having 1-codimensional commutative derived ideal. One subclass in {\Li} was firstly considered and incompletely classified by Sch"obel \cite{Sch93} in 1993. Later, Janisse also gave an incomplete classification of {\Li} and published as a scientific report \cite{Jan10} in 2010. In this paper, we set up a new approach to study the classifying problem of classes {\Li} as well as {\li} and present the new complete classification of {\Li} in the combination with the well-known Eberlein’s result of 2-step nilpotent Lie algebras from \cite[p.,37–72]{Ebe03}. The paper will also classify a subclass of {\li} and will point out missings in Sch"obel \cite{Sch93}, Janisse \cite{Jan10}, Mubarakzyanov \cite{Mub63a} as well as revise an error of Morozov \cite{Mor58}.