Equations not giving the solution

[AngeDieu]

Describe the bug

I study pH in chemistry and I usually need to find a solution to equations of the type x^2/(c0-x)=K, with c0 and K given, x is the advancement of the reaction, between 0 and 1.
About half of the time, the silver doesn't give me the right solution when the search interval is auto (-11 to 11), it gives me something negative. Then I change the search interval to [0,1], and about a quarter of the time, it still doesn't find the solution, which does exist.
This is a big problem because I can't solve such equations by hand and I need the solutions to continue the exercise.

As an example: x^2/(10^(-2)-x)=10^(-0.8)
With auto interval, it only gives me -0.1679273.
With [0,1] interval, it returns "no solution".
GeoGebra gives me both solutions: -0.167927 and 0.009438

To Reproduce

Steps to reproduce the behavior:

1. Go to the Solver app
2. Type the equation
3. Click on solve
4. Only a non satisfying solution (not in [0,1])
5. Change search interval to [0,1]
6. No solutions

Expected behavior

It should give me the solution. (In the example 0.0094)

Environment

Both on N0110 and simulator, epsilon 23.2.5

[adriweb]

(Note that the solution gets found when the interval is [ 0 ; 0.01 ]. Then again, if you don't know in advance where the solution is approximately, it's not like you'll have time to try many intervals...

[adri1numworks]

Thank you for your input, I link this issue to the one already opened internally. This is a complex topic and we try to improve our solver continuously. It might take some time before we solve this specific case. I'll keep you updated

[parisseb]

Install KhiCAS and run
solve( x^2/(10^(-2)-x)=10^(-0.8) )

[AngeDieu]

Well, Khi-CAS isn't available in exam mode with the official firmware, so it isn't a solution.

[parisseb]

Perhaps it's time for educators to ask if they should exclusively rely on company developers (that have their own agenda) or if they should decide themselves what is allowed and what is not allowed in exam? Who is the boss?
KhiCAS is open source, it is very easy to make a specific version where each country could decide which command is available and which command is not, and then ask Numworks to sign this specific version of KhiCAS for the country exam mode.
Or even easier : don't apply exam mode anymore, make a part of the exam without calculator, and another part where all calculators are allowed.