Let's say I wish to use IEEEeqnarray to typeset an equation like the following:

Obviously I can do this by manually inserting lots of spacing commands, but I would prefer to be able to do this by specifying the column alignment when the IEEEeqnarray environment is started. So I have been experimenting with various alignment options such as
\begin{IEEEeqnarray}{lCr}
but can I only achieve an equation typeset similar to

How can I do this through the allignment option?

y=x...left-aligned and+gg..right-aligned? Is youy=x...really that wide? Perhaps a more practical example would be helpful. – Werner Nov 11 '13 at 06:01multlineenvironment fromamsmath. See, e.g., http://tex.stackexchange.com/a/134447/27635 – karlkoeller Nov 11 '13 at 06:05