CAS: solve without simplify fails

[whilealive]

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

[compsystems]

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=so...%5E2+-+49)

(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

.

[parisse]

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.

[whilealive]

Great. Thanks for looking into it.

[compsystems]

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=so...x)%5Ex,+x)

solve(sqrt(x)^x=x^sqrt(x),x)
"Unable to isolate ... hp-prime
list[1.0,4.0] Xcas

[parisse]

Of course more solutions may exist, since bisection may skip over one solution if the step between 2 evaluations is too large.