Real and complex Roots of A cubic equation

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SUMMARY

The discussion focuses on solving the cubic equation y^3 - y + 1 = 0, which has only irrational roots. The rational root theorem indicates that the only possible rational roots, 1 and -1, do not satisfy the equation. To find the exact roots, participants recommend using Cardano's method, a well-established technique for solving cubic equations. For those seeking a quick solution, Wolfram Alpha is suggested as an alternative tool.

PREREQUISITES
  • Understanding of cubic equations and their properties
  • Familiarity with the rational root theorem
  • Knowledge of Cardano's method for solving cubic equations
  • Basic algebraic manipulation skills
NEXT STEPS
  • Study the application of Cardano's method in detail
  • Explore the derivation and use of the cubic formula
  • Practice solving cubic equations using various methods
  • Learn how to utilize Wolfram Alpha for polynomial equations
USEFUL FOR

Students studying algebra, mathematicians interested in polynomial equations, and anyone looking to deepen their understanding of cubic equations and their solutions.

mathsTKK
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Homework Statement


Find the roots of y-y^3=1


Homework Equations





The Attempt at a Solution


Factor theorem doesn't help in this equation. Found from Wikipedia, a very complex formula is needed to solve cubic eq. Can someone show me the steps to find the root?

Thank you ^^
 
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That is the same as y^3- y+ 1= 0. By the "rational root theorem" the only possible rational roots are 1 or -1 and it is easy to see that neither of those satisfy the equation. That is, this equation has only irrational roots. The only way to get exact roots is to use that cubic formula that you cite.
 
Hi mathsTKK! Welcome to PF! :smile:

Since your polynomial does not contain a second order term, you can apply Cardano's method directly. See:
http://en.wikipedia.org/wiki/Cubic_function#Cardano.27s_method

If you want to solve your equation algebraically, this is basically the only way to go.
I won't be able to explain it better than it is already explained in the article.

Of course if you're only interested in a solution, you can always visit http://www.wolframalpha.com.
 

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