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Re: Simplify expression


Hi Muktar,
what you want to do involves assumptions that you must specify. E.g.:

Assuming[x1^2 > x2^2, Sqrt[(x1^2 - x2^2)^2] // Simplify]

will do what you want.
sincerely, Daniel

Mukhtar Bekkali wrote:
> I need to solve system of equations f1[x1,x2]=0,f2[x1,x2]==0, however,
> some elements of these equation have the form Sqrt[(x1^2-x2^2)^2].  It
> takes really long time to solve.  If, however, I manually simplify
> those elements, for example, Sqrt[(x1^2-x2^2)^2]=x1^2-x2^2 then solve
> is fast.  Therefore, the question is how I can force mathematica
> simplify expressions of this sort (another elements are fractions that
> depend on x1 and x2 in Mathematica's mind but in reality they cancel
> out and fraction becomes a number). I do not want to use FindRoot since
> I want to see all solutions. Thanks, Mukhtar Bekkali
> 


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