# [Tutor] faulty code (maths)

Arun Tomar tomar.arun at gmail.com
Sun Nov 23 15:09:54 CET 2008

```hi!

On Sun, Nov 23, 2008 at 5:07 PM, David <ldl08 at gmx.net> wrote:
> Hello everybody,
>
> I recently came across a book by Prof. Langtangen: Indroduction to Computer
> Programming: http://folk.uio.no/hpl/INF1100/INF1100-ebook-Aug08.pdf
>
> I am trying to solve exercise 1.18 ("Why does the following program not work
> correctly?"), but I don't find the mistake: why does the line
>
> q = sqrt(b*b - 4*a*c)

problem here is that the method sqrt doesn't accepts -negative numbers
which in this case is the outcome of the expression above. to rectify
that u can use the following

q = sqrt(math.fabs(b*b - 4*a*c))

basically convert the negative number to absolute number, rest of the
stuff will work.

>
> cause an error? I was playing around with the code, but got nowhere.
>
> Here the entire code:
>
> a = 2; b = 1; c = 2
> from math import sqrt
> q = sqrt(b*b - 4*a*c)
> x1 = (-b + q)/2*a
> x2 = (-b - q)/2*a
> print x1, x2
>
>
> Many thanks for a pointer!
>
> David
> _______________________________________________
> Tutor maillist  -  Tutor at python.org
> http://mail.python.org/mailman/listinfo/tutor
>

--
Regards,
Arun Tomar
blog: http://linuxguy.in
```