Scan your work for any minor typos that could make the rest of the work erroneous. Common examples include misplaced negative signs and parentheses, mistaken numerals, and erroneous operation signs. Skim through the entire process, checking your calculations as you go. This will make any typos stand out.
Check to make sure all of the basic mathematic functions were carried out correctly. With equations that require an extensive number of steps, it is common to make a simple error when working through the calculations quickly. If allowed, use a calculator to quickly double-check all of your calculations to ensure that you carried them out properly.
Compare your work with examples of the equation being worked through, such as those commonly found in the expositional sections of textbooks. This will allow you to compare your work with the established work side-by-side, which makes it easy to locate any errors in the equational process.
Work through the equation from scratch if you are still unable to locate your errors. Do not reference your original work. Instead, rework through the entire calculation process, then compare your results with your first work. By working correctly through the equation the second time, you will easily be able to see where the numbers of the two work processes vary. Study these mistakes you made and take extra care to avoid them when working through future equations.