Sole Cads or Not To CAS

[jonmoore]

(06-09-2022 04:40 PM)C.Ret Wrote:  

(06-09-2022 10:47 AM)tim_crouse Wrote:  According to the tutorial, I'm on Udemy, the answer is -1.

This is the correct answer to the problem.
I get this solution in HOME as well as CAS mode.

In HOME mode, numerical solutions are preferred based on standard 12-digit machine arithmetic.

In CAS mode, by default, the HP Prime first tries to solve the equation symbolically.
In the simple examples, this approach leads to the same simple numerical solution(s). The only advantage of CAS in these cases is the ability to answer exact or exact long integers.
In CAS, the numerical answer can be forced, it is enough to indicate a guessed value for the variable to be solved.

But the real advantage of CAS mode is to used it for step by step symbolic resolutions (see capture).



In jonmoore's screenshot, we can see that he answers another problem where the unknown x is only present in the left side of the equation. That's why he gets a different solution.

Here are screenshots of the original tim_crouse problem in the SOLVE application, real resolution in CAS mode step by step or using the SOLVE command:

I think it's important with any advice we're providing that we go back to the OPs original post where he asks:

Quote:If I am working through algebra problems with 1 or 2 variables how am I to know when I should use the Solver in the CAS menu or the Solver in the Apps Menu ( the command line function not the actual app)?

In general, when it comes to basic algebra problems that would normally be solved symbolically by hand, I believe that first attempting to use the solve function in the CAS is the best approach because it only provides exact answers unless you force it for a numeric answer by including a decimal point in at least one of the numeric constants.

In this instance, the OP is going through a Udemy course, but he could just as easily have been a high school student checking his answers on the Prime and basic algebra problems like the example in this thread are the basis for teaching symbolic manipulation in high school. The last thing the student needs is to provide a floating-point answer when a rational answer would be the true result when the problem is solved symbolically.