+- HP Forums (https://www.hpmuseum.org/forum)
+-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html)
+--- Forum: HP Prime (/forum-5.html)
+--- Thread: Problem with 2nd order polynomial (/thread-22359.html)
Problem with 2nd order polynomial - ktomp - Yesterday 08:19 AM
Hello everyone,
I got an exam the other day and to my surprise my HP prime (G1 hardware) failed to solve a 2nd order polynomial (a*x^2+b*x+c = 0) with the following coefficients:
a = 30188156.0038281
b = -12497373621.6526
c = 1058636761186.350
I was in CAS mode and tried using the Solve, Zeros, Numerical Solve but only got empty brackets as a result (like []). Same thing happens even with the latest update of 2024/09.
It's probably due to the fact that the coeffecients of the polynomial where quite large numbers, cause when I divided everything with the "a" coefficient and the polynomial became x^2+(b/a)*x+(c/a) all the functions managed to find the roots correctly.
Could this be a bug?
Many thanks for your help
RE: Problem with 2nd order polynomial - Patocuy - Yesterday 01:16 PM
Hi.
I used proot and solve and got the same solutions with both functions, perhaps solve needs to know which variable you are solving for.
UPDATE
Now I used the same syntax as you, without specifying the variable to solve for and got the same solutions as before. You could use purge(x) to be sure that x has no value assigned and check your CAS settings, I have attached mine so you can compare.
Regards
RE: Problem with 2nd order polynomial - ktomp - Today 06:58 AM
Hi, thanks for trying to help me out.
I only managed to get solutions with proot() function. Solve() won't return solutions regardless of the syntax. I even purged x just to be sure, but to no avail.
RE: Problem with 2nd order polynomial - C.Ret - Today 02:53 PM
Hi guys!
Just look at this and compare:
What are your conclusions or assumptions? Are they the same as the one I just made?
How did the CAS-solve statement work out numerically compared to other specific and only numeric functions?
Did you understand what happened with CAS-solve when an interval is given for the numerical variable x? Why this works in the first case?
Hope this helps you a little.
And that the prankster HP Prime didn't ruin all of ktomb 's hopes of passing his exam!
RE: Problem with 2nd order polynomial - Liamtoh Resu - Today 06:16 PM
I have been trying to understand this thread.
How can the estimates for x be obtained without running proot first?
There are significant differences of values for 'c' in the two images b C.Ret.
Why are there differences between the two solve answers.
What are the answers to the questions that C.Ret posed?
I hhave limited experiences with the type of problem that ktomb asked on the prime.
Thanks.