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Student Support Forum: 'Solving Polynomials' topicStudent Support Forum > General > "Solving Polynomials"

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Peter Pein
09/25/09 5:48pm

oops I forgot sth.:

When you are happy with the approximate solutions, NSolve is much faster than Solve:

In[4]:= appr=NSolve[x^3 + x^2 - 8*x + 1 == 0, x]
Out[4]= {{x -> -3.422698602651092},
{x -> 0.1272828790601753},
{x -> 2.2954157235909167}}

but keep in mind that these are not solutions ("sol" is the exact solution from my last posting):

In[6]:= FullSimplify[x^3 + x^2 - 8*x + 1 /. {sol, appr}]
Out[6]= {{0, 0, 0},
{3.552713678800501*^-15,
6.591949208711867*^-17,
-3.552713678800501*^-15}}

Peter


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Subject (listing for 'Solving Polynomials')
Author Date Posted
Solving Polynomials Nick 09/19/09 4:58pm
Re: Solving Polynomials TomD 09/21/09 6:32pm
Re: Solving Polynomials yehuda ben-s... 09/22/09 08:31am
Re: Solving Polynomials Peter Pein 09/25/09 5:41pm
Re: Solving Polynomials Peter Pein 09/25/09 5:48pm
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