# Auto-simplification: CAS does, Calc Suite doesn't

Mike Dekker shared this question 2 months ago

In the CAS Calculator, if I define f(x) = (x^2-1)/(x-1), it automatically simplifies to x+1, and if you compute f(0) you get 1.

In the Calculator Suite, making the same definition, there's no simplification done and f(0) is undefined (as it should be).

Why the difference? Why does the CAS auto-simplify? Can I turn that off?

Similar questions from 5+ years ago led to using the "KeepInput" command which doesn't seem to exist anymore. ????

1

I trust you mean f(1), since f(0) is defined in both cases. Why is it that you want the unsimplified version? Surely in this case, the CAS version is the 'better' method and the Calculator Suite is "wrong", given that the function does not have an asymptote. Wouldn't you want the Calculator Suite to simplify, rather than the other way around?

1

Bah, yes, I meant f(1). As defined, f(x) is a classic example of a function with a removable discontinuity, and is the sort of expression you end up with when using the definition of a derivative. I'd hoped to illustrate that to my students in an assignment, but the usefulness of it disappears when the CAS auto-simplifies. In terms of taking limits and doing algebra, auto-simplification glosses over steps students would need to take when doing it by hand, so I'd rather have it stay as defined and manually simplify if necessary.

1

Classic CAS and new CAS both autosimplify:

Graphing Calculator and Classic Algebra View don't. Sorry, there are no plans to add options for that

1

OK - thanks for the input. I'm still figuring out what's best for students to use, given that there are new and old versions of these apps.