## LaTeX forum ⇒ Math & Science ⇒ Equation system not working as I want to

Information and discussion about LaTeX's math and science related features (e.g. formulas, graphs).
MathiasHan
Posts: 3
Joined: Mon Oct 01, 2018 11:46 am

### Equation system not working as I want to

Hi folks,

I am kinda new to LaTeX and trying to build a presentation with some math.

I want to write these two equations, but not quite sure how to do it:

As for equation number (1) I am wondering on how I allign the equations meanwhile I just keep equation 1 and not equation 1 and 2 My code is currently:
\begin{eqnarray}F_{t+1} &=& F_t+F_t*(R_{t+1}-1)(1-\tau_{PAL})+\theta Y_{t+1} \\&=& \theta Y_{t+1}+F_t(\tau_{PAL}+R_{t+1}(1-\tau_{PAL})),\end{eqnarray}

, but this results with equation 1 and 2 whereas it should only be 1.

For equation number 4 I am not sure which codes to use

Can anyone help me? Best regards MathiasH
Attachments Hjælp LaTeX.JPG (18.98 KiB) Viewed 732 times

Stefan Kottwitz
Posts: 9504
Joined: Mon Mar 10, 2008 9:44 pm
Hi Mathias,

welcome to the forum!

Here is a way:

\documentclass{article}\usepackage{amsmath}\begin{document}\begin{equation}  \begin{split}    F_{t+1} &= F_t+F_t*(R_{t+1}-1)(1-\tau_{PAL})+\theta Y_{t+1} \\            &=  \theta Y_{t+1}+F_t(\tau_{PAL}+R_{t+1}(1-\tau_{PAL})),  \end{split}\end{equation} \end{document}

Never use eqnarray (any more), since that is not optimal. Better use align or any other environment of the amsmath package.

Stefan

Johannes_B
Site Moderator
Posts: 4078
Joined: Thu Nov 01, 2012 4:08 pm
What is shown in the figure as equation four can be done using the cases environment of package amsmath.
The smart way: Calm down and take a deep breath, read posts and provided links attentively, try to understand and ask if necessary.

MathiasHan
Posts: 3
Joined: Mon Oct 01, 2018 11:46 am
Thank you!!!

However, now I am stuck on this line which is normal text. Anyone have any clue on how to write it?

"If we let $\mathbf{\mu}(t+1)$ be the vector of the expected returns in year t+1 and let $\sum_=$" clearly does not work.
Attachments help latex 2.JPG (15.71 KiB) Viewed 707 times

Stefan Kottwitz
Posts: 9504
Joined: Mon Mar 10, 2008 9:44 pm
Stuck with which detail? What does not work? Making bold? Then use \boldsymbol{\mu}.

Stefan

MathiasHan
Posts: 3
Joined: Mon Oct 01, 2018 11:46 am
Thanks! That one works perfectly now. Any idea of how I do the sigma with 2 lines under? Such a great help!

Stefan Kottwitz
Posts: 9504
Joined: Mon Mar 10, 2008 9:44 pm
I guess that's the easiest straightforward way:

\documentclass{article}\begin{document}$\underline{\underline{\sum}} x$\end{document}