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CAS: solve without simplify fails - whilealive - 07-10-2017 04:11 PM
Please excuse me if this has been answered here before. I couldn't find any thread referring to this yet.
In CAS:
solve((x-7)*(x+7) = x^2 - 49) --> [undef]
solve(simplify((x-7)*(x+7) = x^2 - 49)) --> {x}
Firmware: 20160829 (10637)
Please understand that for pupils it is hard to enter nested commands. Is there any other way to solve this directly?
Many thanks in advance.
Bruno
RE: CAS: solve without simplify fails - compsystems - 07-10-2017 05:05 PM
is very interesting that with the simplification of the expression, Xcas can calculate it, the good thing that Bernard Parisse (BP), could improve the command to solve without needing to simplify
{X} means that x = x, that is, it takes all the values of the real numbers
https://www.wolframalpha.com/input/?i=solve((x-7)*(x%2B7)+%3D+x%5E2+-+49)
![[Image: casio_classpad_on_pc_image00.png]](http://eonicasys.com.co/public/math/CAS/classPAD/images/casio_classpad_on_pc_image00.png)
(07-10-2017 04:11 PM)whilealive Wrote: P.. for pupils it is hard to enter nested commands.Standard notation not RPN or PN involves nesting orders (cmds) within orders
.
RE: CAS: solve without simplify fails - parisse - 07-11-2017 01:11 PM
Normally you don't need to simplify before solving. But here there is special code to solve linear equations a*x+b=0 and it does not contain simplification for a, I will improve that. Never seen this before, because nobody ever tried to solve 0=0 with that kind of input.
RE: CAS: solve without simplify fails - whilealive - 07-11-2017 06:55 PM
Great. Thanks for looking into it.
RE: CAS: solve without simplify fails - compsystems - 07-11-2017 07:33 PM
A similar expression
solve( x^(x^x)=(x^x)^x, x)
list[ 2.0 ]
"Unable to isolate ... hp-prime
Root x = 1 was not found on Xcas, please show "More solution may exist"
https://www.wolframalpha.com/input/?i=solve(+x%5E(x%5Ex)%3D(x%5Ex)%5Ex,+x)
solve(sqrt(x)^x=x^sqrt(x),x)
"Unable to isolate ... hp-prime
list[1.0,4.0] Xcas
RE: CAS: solve without simplify fails - parisse - 07-12-2017 05:39 AM
Of course more solutions may exist, since bisection may skip over one solution if the step between 2 evaluations is too large.