\left. and \right. fixes issues with a missing delimiter (parenthesis) since LaTeX can only look at one line at a time. However, if the lines have different heights, the parentheses don't match. In such a case one can insert a suitable \vphantom, or use \bigl( ... \bigr), \Big, \bigg, etc.Learn LaTeX easily with newest books:
The LaTeX Beginner's Guide: 2nd edition and perfect for students writing a thesis
The LaTeX Cookbook: 2nd edition full of practical examples for mathematics, physics, chemistry, and more
LaTeX Graphics with TikZ: the first book about TikZ for perfect drawings in your LaTeX thesis
Learn LaTeX easily with newest books:
The LaTeX Beginner's Guide: 2nd edition and perfect for students writing a thesis
The LaTeX Cookbook: 2nd edition full of practical examples for mathematics, physics, chemistry, and more
LaTeX Graphics with TikZ: the first book about TikZ for perfect drawings in your LaTeX thesis