Factoring Polynomials

[Russ P.]

On Dec 18, 6:41 pm, "Russ P." <Russ.Paie... at gmail.com> wrote:
> On Dec 18, 6:31 pm, Collin D <collin.da... at gmail.com> wrote:
>
>
>
> > On Dec 18, 6:27 pm, Collin D <collin.da... at gmail.com> wrote:
>
> > > On Dec 18, 6:23 pm, "Russ P." <Russ.Paie... at gmail.com> wrote:
>
> > > > On Dec 18, 6:17 pm, Collin D <collin.da... at gmail.com> wrote:
>
> > > > > On Dec 18, 6:12 pm, Collin D <collin.da... at gmail.com> wrote:
>
> > > > > > On Dec 18, 11:37 am, collin.da... at gmail.com wrote:
>
> > > > > > > I am trying to write a simple application to factor polynomials. I
> > > > > > > wrote (simple) raw_input lines to collect the a, b, and c values from
> > > > > > > the user, but I dont know how to implement the quadratic equation
>
> > > > > > > x = (-b +or- (b^2 - 4ac)^1/2) / 2a
>
> > > > > > > into python. Any ideas?
>
> > > > > > I completed the code:
>
> > > > > > #import
> > > > > > from math import sqrt
>
> > > > > > # collect data
> > > > > > a = float(raw_input('Type a value: '))
> > > > > > b = float(raw_input('Type b value: '))
> > > > > > c = float(raw_input('Type c value: '))
>
> > > > > > # create solver
> > > > > > def solver(a,b,c):
> > > > > >     if b**2 - 4*a*c < 0:
> > > > > >         return 'No real solution.'
> > > > > >     else:
> > > > > >         sol1 = -1 * b + (sqrt(b**2 - 4*a*c)) / 2*a
> > > > > >         sol2 = -1 * b - (sqrt(b**2 - 4*a*c)) / 2*a
> > > > > >         return (sol1, sol2)
>
> > > > > > # execute
> > > > > > print solver(a,b,c)
>
> > > > > > Thanks to everyone who helped...
> > > > > > This really expanded my knowledge on some of the mathematical
> > > > > > functions in Python.
>
> > > > > UPDATE:
> > > > > '
>
> > > > > #import
> > > > > from math import sqrt
>
> > > > > # collect data
> > > > > a = float(raw_input('Type a value: '))
> > > > > b = float(raw_input('Type b value: '))
> > > > > c = float(raw_input('Type c value: '))
>
> > > > > # create solver
> > > > > def solver(a,b,c):
> > > > >     if b**2 - 4*a*c < 0:
> > > > >         return 'No real solution.'
> > > > >     else:
> > > > >         sol1 = (-1 * b + (sqrt(b**2 - 4*a*c))) / 2*a
> > > > >         sol2 = (-1 * b - (sqrt(b**2 - 4*a*c))) / 2*a
> > > > >         return (sol1, sol2)
>
> > > > > # execute
> > > > > print solver(a,b,c)
>
> > > > You need to put your denominator, 2*a, in parens. The way it stands,
> > > > you are dividing by 2, then multiplying by a. That's not what you
> > > > want.
>
> > > > Also, for better style, I suggest you compute the discriminanat once
> > > > and store it for reuse rather than repeating the expression three
> > > > times.- Hide quoted text -
>
> > > > - Show quoted text -
>
> > > I see what you mean on the denominator and discriminant. Ill do that.- Hide quoted text -
>
> > > - Show quoted text -
>
> > UPDATE:
>
> > #import
> > from math import sqrt
>
> > # collect data
> > a = float(raw_input('Type a value: '))
> > b = float(raw_input('Type b value: '))
> > c = float(raw_input('Type c value: '))
>
> > # find discriminant
> > disc = b**2 - 4*a*c
>
> > # create solver
> > def solver(a,b,c):
> >     if disc < 0:
> >         return 'No real solution.'
> >     else:
> >         sol1 = (-1 * b + (sqrt(disc))) / (2*a)
> >         sol2 = (-1 * b - (sqrt(disc))) / (2*a)
> >         return (sol1, sol2)
>
> > # execute
> > print solver(a,b,c)
>
> A couple of style points. I would use -b rather than -1 * b. Also, you
> don't need the else clause. You can simplify it to
>
> def solver(a, b, c):
>
>     disc = b**2 - 4 * a * c
>
>     if disc < 0: return "No real solution."
>
>     sol1 = (-b + sqrt(disc)) / (2*a)
>     sol2 = (-b - sqrt(disc)) / (2*a)
>
>     return sol1, sol2

By the way, this little function is suitable for your purposes here,
but it is not really a good general quadratic solver, because it
returns different types depending on the inputs. For a good general
function, you would probably want to throw an exception when the
discriminant is negative (as an earlier poster suggested).