System of equations on HP Prime
03-08-2019, 12:09 PM (This post was last modified: 03-08-2019 01:58 PM by fpicoral.)
Post: #1
 fpicoral Junior Member Posts: 4 Joined: Mar 2019
System of equations on HP Prime
Hello everyone!
How can I solve systems of equations on the HP Prime, i.e., what should I do to get x=-1 and y=11 from the system below:

3x+y=8
x+2y=21

Edit:
Add both equations on the Solve app and solve both ate the same time.
03-08-2019, 02:26 PM
Post: #2
 swagner53 Junior Member Posts: 11 Joined: Jun 2018
RE: System of equations on HP Prime
Hi,

There is a nifty App called "Linear Solver" that works great on systems of 2 or 3 equations. For anything greater, there are a couple of ways, but perhaps the easiest way is the use the RREF() command, taking a 2x3 matrix of the coefficients.

Good luck and take care,

Steve
03-08-2019, 04:00 PM (This post was last modified: 03-08-2019 04:06 PM by DrD.)
Post: #3
 DrD Senior Member Posts: 1,095 Joined: Feb 2014
RE: System of equations on HP Prime
One way:
[CAS]
solve({(3*x+y) = 8,(x+2*y) = 21},{x,y})

Another way:
[CAS]
col(RREF([[3,1,8],[1,2,21]]),3)
03-08-2019, 04:27 PM
Post: #4
 ThomasA Junior Member Posts: 23 Joined: May 2014
RE: System of equations on HP Prime
Hello,
there is an app for small systems of linear equations (2 unknowns in 2 equations and 3 unknowns in 3 equations). You find it by pressing Apps and tapping on Linear Solver.
Hope that helps
Thomas
03-08-2019, 06:14 PM (This post was last modified: 03-08-2019 06:14 PM by Joe Horn.)
Post: #5
 Joe Horn Senior Member Posts: 1,523 Joined: Dec 2013
RE: System of equations on HP Prime
My favorite way to solve linear systems is an efficient way on the keyboard: just a single division. The example below is the system you gave above. The screen capture on the left is with Textbook Display Mode turned on, and the one on the right is with it turned off, otherwise they are identical.

This nifty method works with any size system. Just be sure to use single square bracket for the numerator (which contains the constants from the right side of the equations) and double square brackets for the denominator (which contains the coefficients from the left side of the equations). If your Prime flashes a warning at you, saying something like "This shortcut is a Bad Thing which we included only under pressure from users of previous HP calculator models", ignore it.

<0|ɸ|0>
-Joe-
03-08-2019, 09:48 PM
Post: #6
 fpicoral Junior Member Posts: 4 Joined: Mar 2019
RE: System of equations on HP Prime
Thanks for all the help guys!

One more thing: how can I do a inequalities system?

I'm trying to solve this one and I did not manage to do so:

y ≤ 3x+1
x-y > 1
03-08-2019, 10:48 PM
Post: #7
 DrD Senior Member Posts: 1,095 Joined: Feb 2014
RE: System of equations on HP Prime
I think the Advanced Graphing app handles inequalities nicely. A couple of things to notice though:

1. Separate implicit multiplications: y ≤ 3x+1 should be: Y ≤ 3*X+1, etc.
2. Using the apps requires UPPER case variables!
y ≤ 3x+1 ==> Y ≤ 3*X+1

Enter your equations with those two changes into the Advanced Graphing app [Symb] page, and then use the [Plot] page to view your results.
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