# Changing size of parentheses using \left and \right

What's wrong with this?

$$\partial{Q}=\frac{1}{2}\frac{\sum{h_f}}{\sum \left({\frac{h_{fi}}{Q_i}\right)}}$$


I keep getting errors.

• (1) Welcome, (2) Next time please provide a full minimal example, that others can just copy and use. (3) Please cite the error you get – daleif Jul 20 '16 at 15:36
• It should be }\right) instead of\right)} (in my opinion, the corresponding pair of braces isn't necessary). – Bernard Jul 20 '16 at 16:13

Make sure that you have put the curlybraces at the correct position. Also, the pair causing problems here, doesn't do anything here, so I suggest just removing it.

When there are lots of groups like {} and such, It gets difficult to see the where each group begins and ends. Try to add some space between, to ease the reading. Spaces are ignored in math-mode, so you can use as much as you want.

I have added two suggestions on how you could make it easier to read. The first simply adds some single-spaces here and there, while the other one adds linebreaks and indentation. This is probably overkill fo this example, but for complex formulas and programming, it is really a must. Both of them produces the same ouput.

Output

Code

\documentclass[11pt]{article}
\usepackage{mathtools}
\begin{document}
$$\partial{Q} = \frac{1}{2} \frac{ \sum{h_f} }{ \sum \left( \frac{ h_{fi} }{ Q_i } \right)}$$

$$% Same code, just formated for ease of reading. Overkill. \partial{Q} = \frac{1}{2} \frac{ \sum{h_f} }{ \sum \left( \frac{ h_{fi} }{ Q_i } \right) }$$
\end{document}

• My editor checks {} () and []. It's getting \begin \end and \if \fi to match up that gives me problems. Sometime I have to add braces around environments just to find the problem. – John Kormylo Jul 20 '16 at 16:00