I am relatively new working with LaTeX and I don't know how to solve this problem.

I have several equations that I wrote in a general form, but when writing them, I want to show that the general form is just a generalization for three specific formulas; i.e.

I have this

but I want to have this:

P.S: I could use the command tag like in this post Customize equation numbering for Equation environment?, but I have over 60 equations and I could not use the command tag for each line individually (Also, there could be multiple errors doing it manually) Can someone help me please?

My MWE is:

 \documentclass[a4paper,12pt]{article} \usepackage[spanish]{babel} \usepackage[latin1]{inputenc} \usepackage{amsmath} \begin{document} \begin{equation} E=mc^2 \end{equation} \end{document} 

I am relatively new working with LaTeX and I don't know how to solve this problem.

I have several equations that I wrote in a general form, but when writing them, I want to show that the general form is just a generalization for three specific formulas; i.e.

I have this

but I want to have this:

P.S: I could use the command tag like in this post Customize equation numbering for Equation environment?, but I have over 60 equations and I could not use the command tag for each line individually (Also, there could be multiple errors doing it manually) Can someone help me please?

My MWE is:

 \documentclass[a4paper,12pt]{article} \usepackage[spanish]{babel} \usepackage[latin1]{inputenc} \usepackage{amsmath} \begin{document} \begin{equation} E=mc^2 \end{equation} \end{document} 

EDIT: For more clarity, I put some equations with subscript (j) and others not; and those with subscript I want to be counted not as just one equation; but from n (number of previous equation) to j (from 1 to 3).I know how to set this MANUALLY, but that wouldn't be efficient nor exent of mistakes since we are talking of over 100 equations in different sections). An example is:

My MWE is the following:

\begin{document} \begin{equation} F=ma \end{equation} \begin{equation} E=m_{j}c^2 \tag{2), (3), (4} \end{equation} \setcounter{equation}{4} \begin{equation} A=B+C \end{equation} \begin{equation} D_{j}= E_{j} + F_{j} \tag{6), (7), (8} \end{equation} \end{document} 

I am relatively new working with LaTeX and I don't know how to solve this problem.

I have several equations that I wrote in a general form, but when writting them, I want to show that the general form is just a generalization for three specific formulas; i.e.

I have this

but I want to have this:

P.S: I could use the command tag like in this post Customize equation numbering for Equation environment?, but I have over 60 equations and I could not use the command tag for each line individually (Also, there could be multiple errors doing it manually) Can someone help me please?

My MWE is:

 \documentclass[a4paper,12pt]{article} \usepackage[spanish]{babel} \usepackage[latin1]{inputenc} \usepackage{amsmath} \begin{document} \begin{equation} E=mc^2 \end{equation} \end{document} 

I am relatively new working with LaTeX and I don't know how to solve this problem.

I have several equations that I wrote in a general form, but when writing them, I want to show that the general form is just a generalization for three specific formulas; i.e.

I have this

but I want to have this:

P.S: I could use the command tag like in this post Customize equation numbering for Equation environment?, but I have over 60 equations and I could not use the command tag for each line individually (Also, there could be multiple errors doing it manually) Can someone help me please?

My MWE is:

 \documentclass[a4paper,12pt]{article} \usepackage[spanish]{babel} \usepackage[latin1]{inputenc} \usepackage{amsmath} \begin{document} \begin{equation} E=mc^2 \end{equation} \end{document}