prime factor

[TylerTexas]

When I am in CAS mode and type in factor(x^2-25) it returns -24. I want it to return (x+5)(x-5). I do not understand why it is not returning (x+5)(x-5). 

[TylerTexas]

Delete the CAS variables to make it start working again.

[andy11]

Try to check "exact mode" in CAS settings (if it is unchecked of course)

[Maké]

Hi!, TylerTexas:

Welcome, to Forum!.

This is only for use with CAS.

In Setting CAS, change Exact by Approximate.

[Tim_Wessman · Accepted solution]

If you are not typing a lower case "x", please use the lower case "x" and not upper case. Most likely you have an upper case X (which will contain a value of 0 - thus you get 0^2-25 which is -24...)

If you are typing lower case, type the command "purge(x)" to delete the number you have stored in x. If you have a value stored in there, the number is being put into your equation first and thus you have no more x values left to factor because they've been replaced.

[TylerTexas]

Also, when I push the "x t theta n" button,  I sometimes get something besides lower case x, which might be what caused the problem with not factoring. How do I change what the "x t theta n" displays when pressed? 

[Tim_Wessman]

The X T Theta N key returns the current "independent" variable for you active application. Normally, this will be X (or x in the CAS). However, when you have the polar app, it will be the theta. Sequence will be N, and parametric will be T. These are the variables that are used in those application for the currently changing variable during plot and whatnot.

If you want to use one of those specific values, change your current application by pressing apps, tapping the one you want, and then go back to home, cas, symb, etc. In most cases, just pressing <alpha> <letter> will be quick enough for you I think though.