Customizing displayed formulas

There are two options that modify the way the formulas are displayed:

fleqn	"left equation numbers"	This causes all displayed formulas to be aligned at the left margin.
leqno	"left equation numbers"	All numbered formulas would get the numbers on the left side instead of the right.

Often, formulas are not displayed just standalone. We may encounter situations where:

• A formula is too long to fit on one line

• Several formulas are listed row-by-row

• An equation shall be transformed step-by-step

• A chain of inequalities spans over more than one line

• Several formulas shall be aligned at relation symbols

We may also encounter similar situations, where we have to write multi-line formulas, often with some kind of alignment. The amsmath package offers specialized environments for nearly every such need.