How to write simulataneous system of linear equations?

Question

I have simultaneous system of linear equations. I want to eliminate the one variable to get the other. I don't know how to write them in LaTeX in form shown in picture below I have taken:

What have you tried so far? Please add a minimal working example (MWE) of your current code. — epR8GaYuh, Apr 06 '20 at 09:49
@epR8GaYuh I do not know how to write then how could I try, I know how to wirte equaton but don't know how to draw a line below them and changing the sign and then add. — Noor Aslam, Apr 06 '20 at 09:52
Here there is a start point: https://tex.stackexchange.com/questions/254261/how-can-you-draw-a-horizontal-line-inside-an-align-environment — Sebastiano, Apr 06 '20 at 09:55
@Sebastiano In site you have mentioned brother, he is adding, in case of subtraction how to change the signs below ? — Noor Aslam, Apr 06 '20 at 10:08
The layout in the screenshot you provided is not that great. Do you need to reproduce this substandard layout, or might you be open to a better solution? — Mico, Apr 06 '20 at 10:11

score 5 · Accepted Answer · answered Apr 06 '20 at 11:30

Here's how I would typeset the equations at hand -- not exactly identical to the screenshot you posted. I make no excuse for the resulting discrepancy.

\documentclass{article}
\usepackage{newtxtext,newtxmath} % optional
\usepackage{booktabs} % for '\midrule' macro
\usepackage{array}    % for '\newcolumntype' macroi
\newcolumntype{C}{>{{}}c<{{}}} % col. type for binary and relational symbols
\newcommand\mr[1]{\multicolumn{3}{r}{#1}} % handy shortcut macro

\begin{document}
Subtracting equation (3) from equation (4), we have
\[
\setlength\arraycolsep{0pt}
\begin{array}{lrCrCrCl}
              & 5(2-i)z &+& 10iw   &=& -5 &+& 5i\\
(-)\mkern18mu & 5(2-i)z &-& (7-i)w &=& 13 &-& 9i\rlap{\,.}\\
\midrule
            & \mr{10iw+(7-i)w} &=& -18 &+& 14i\\
\Rightarrow & \mr{(7+9i)w}     &=& -18 &+& 14i
\end{array}
\]
\end{document}

How to write simulataneous system of linear equations?

1 Answers1