Simplify quirk

[dah145]

(11-11-2020 05:25 PM)parisse Wrote:  That's because the main variable of the polynomial is a here. You can run reorder to specify variable ordering.

I see, thanks.

Another pet peeve of mine with this calculator is how the poly2sym() output is handled, when compared to other software such as matlab for example, which I think is more intuitive:


syms a b c d x
p = poly2sym([1, a, b + c, d], x)

Outputs:

p = x^3 + a*x^2 + (b + c)*x + d

In HP Prime, you would expect a result with grouping by coefficient order but this not the case:

p:=poly2sym([1, a, b+c, d]) = x*(x*(a+x)+b+c)+d
and after a simplify press: a*x^2 + b*x + d + x^3

Now as there's no built in function to group a polynomial by coefficient order, one way around to do it in the HP Prime is:

sum(coeff(p,x).*seq(x^n,n,degree(p,x),0,1)) = a*x^2 + x^3 +x*(b+c) + d (Result with simplify minimum in CAS settings)

A reorder command would give me the correct descending exponential order for variable x but would expand the polynomial.

The only way to get sum(coeff(p,x).*seq(x^n,n,degree(p,x),0,1)) =x^3 + a*x^2 + +x*(b+c) + d is to have the simplify setting set to none.