I see this request a *lot* on here, and the usual answer is usually to avoid even trying to do this, but it’s such a useful thing to be able to do and so many people continue to ask for it, I came up with something I think will effectively do this for most people.

**Problem**

You want to check if a student’s algebra is correct. So maybe they’re rewriting something, maybe factoring a quadratic, maybe expanding, possibly something much more complex such as simplifying the sum of several rational expressions.

This is borderline impossible to do. There are just too many equivalent ways of writing expressions.

**Solution**

- Create a robust data table whose output corresponds to the student’s answer expression
- Compare the data set to that data set formed by the initial expression
- Check that the difference in residual totals goes to zero(or as the limit approaches zero if you prefer some flexibility when it comes to certain situations)
- Rinse and repeat

**Caveat**

There are are edge-cases I can imagine that might not work so well with this but let me know what you think!

Here’s an activity that does what I’m talking about: Equivalent Expression Check | Question Bank