# Missing delimiter (. inserted) .<to be read again>- : Can't write curly brackets [duplicate]

I'm trying for so long now to write this

$\displaystyle{ x = \Big{ -\frac{b}{2} + \sqrt{\frac{a^3}{27} + \frac{b^2}{4}} \Big}^{\frac{1}{3}} + \{-\frac{b}{2} - \sqrt{\frac{a^3}{27} + \frac{b^2}{4}} \}^{ \frac{1}{3}} }$


The problem is it won't accept me adding those curly brackets in any form, be it

\{ \}
\left{ \right}
\Big{  \Big}


etc. Without adding curly braces visible in the output, it works fine

These are all my packages

\documentclass[12pt]{article}

\usepackage{amsmath} % allows piecewise functions
\usepackage{amsfonts} % allows using additional font commands
\usepackage{amssymb} % for varpropto - proportion symbol
\usepackage{graphicx} % include graphics / image package
\usepackage{fullpage} % page formatting
\usepackage{mathtools} % needed for under / over braces
\usepackage{textcomp} % needed for \sim (tilde) and \texttildelow
\usepackage{amssymb} % for (small)setminus
\usepackage{mathrsfs} % for caligraphic letters
\usepackage[normalem]{ulem} % for underlining \uline{}

\usepackage[utf8]{inputenc}
%\usepackage[T1]{fontenc} % OT1 (Old Text encoding) = not a good idea to have
\usepackage[greek, english]{babel}
\usepackage{lmodern}


I cannot get past this sentence after almost 1 hour of troubleshooting! What's wrong? I'm using TexMaker. Thanks in advance!

## marked as duplicate by egreg, David Carlisle, Jesse, Stefan Pinnow, user13907 Jan 12 '17 at 12:45

• \displaystyle does not take an argument so \displaystyle{...} should be \displaystyle ... otherwise the spurious {} prevent white space stretching and prevents line breaking, but why use $\displaymath...$ rather than real display math $...$ ? – David Carlisle Jan 12 '17 at 11:44
• Apparently \displaystyle works both ways. That wasn't the issue. Thanks though. – Nikos Jan 12 '17 at 11:46
• No it does not work both ways. the {} in the above are unrelated to \displaystyle and destroy the inline white space behaviour as I said. It doesn't address your question which is why I left as a comment not an answer. – David Carlisle Jan 12 '17 at 11:47

There are no

\left{ \right}
\Big{  \Big}


They should be

\left\{ \right\}
\Bigl\{  \Bigr\}


Please observe \Bigl and \Bigr, not simply \Big, which gives different spacing.