HP Forum Archive 21

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HP 50g - collect by powers of x Message #1 Posted by Juraj O. on 17 Feb 2013, 4:40 a.m. Is there an easy way to collect terms by powers of a variable in an expression? Ie. I have an expression on the stack that looks like this A*x^2 + A*x + B*x + C I want to group (something like GROUP(expression,'x') ) it by powers of x, so that it looks like this: Ax^2 + (A+B)x + C and not something like A(x^2 + x) + Bx + C which FACTOR/SIMPLIFY/COLLECT often give me. It would also be handy if I could extract a vector of coefficients from that expression: [A A+B C]. If anyone knows how to do this please help me out :)

Re: HP 50g - collect by powers of x Message #2 Posted by Juraj O. on 17 Feb 2013, 5:11 a.m., in response to message #1 by Juraj O. I think I've found what I was looking for - the function A->P from the Polynomial library by Steen S. Schmidt.

Re: HP 50g - collect by powers of x Message #3 Posted by Ronald Williams on 17 Feb 2013, 9:50 a.m., in response to message #1 by Juraj O. For A*X^2 + A*X + B*x + C try using COLLECT alone and you should get A*X^2 + (B+C)*X + C as desired.

Re: HP 50g - collect by powers of x Message #4 Posted by Mike Morrow on 17 Feb 2013, 10:38 a.m., in response to message #3 by Ronald Williams Quote: For A*X^2 + A*X + B*x + C try using COLLECT alone and you should get A*X^2 + (B+C)*X + C as desired. That would be quite remarkable!

Re: HP 50g - collect by powers of x Message #5 Posted by Ronald Williams on 17 Feb 2013, 3:57 p.m., in response to message #4 by Mike Morrow I'm using a real HP50g with rom 2.15 and flag settings as follows: { # 80800002452103F0h # 0h # 8018000002000010h # 0h } and COLLECT works for me!

Re: HP 50g - collect by powers of x Message #6 Posted by Mike Morrow on 17 Feb 2013, 4:25 p.m., in response to message #5 by Ronald Williams I doubt that any HP 50G will indicate that A*X^2 + A*X + B*X + C = A*X^2 + (B+C)*X + C as your message number 3 in this thread proposes. :-) (unless A = C) Edited: 17 Feb 2013, 4:38 p.m.

Re: HP 50g - collect by powers of x Message #7 Posted by Gerson W. Barbosa on 17 Feb 2013, 4:26 p.m., in response to message #5 by Ronald Williams He was talking about the typo: A*X^2 + (B+C)*X + C instead of A*X^2 + (A+B)*X + C.

Re: HP 50g - collect by powers of x Message #8 Posted by Ronald Williams on 17 Feb 2013, 6:57 p.m., in response to message #5 by Ronald Williams Good catch! Thank you Gerson I did miss type the expression. As you correctly pointed out it should have been A*X^2 + (A+B)*X + C and Mike I missed your subtle humor in post #4.

Re: HP 50g - collect by powers of x Message #9 Posted by Juraj O. on 17 Feb 2013, 7:16 p.m., in response to message #1 by Juraj O. I was wondering one more minor thing which doesn't really deserve its own thread. Is it possible in the equation editor, with an expression already entered, to add a factor or a summand on the beginning, from the left? Ie. we have b•c. Is it possible to multiply it by a from the left, so we have a•b•c? Same question for b+c, so we get a+b+c?

Re: HP 50g - collect by powers of x Message #10 Posted by C.Ret on 18 Feb 2013, 5:09 a.m., in response to message #1 by Juraj O. Hi, On my HP-28S, 'A*x^2 + A*x + B*x + C' x 2 TAYLR returns 'C + (A+B)*x + A*2/2*x^2' then a simple COLCT leads to '(A+B)*x + A*x^2 + C' Is that expression close enough to the expected format? Edited: 18 Feb 2013, 5:11 a.m.

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