Solution of a depressed cubic equation

  • Thread starter PainterGuy
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  • #1
PainterGuy
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Hi,

I was trying to solve the equation x³-2x-5=0. I solved it online and the real solution is x≈2.0946.

The following is an excerpt from the Wikipedia article on cubic equation.

1592807371902.png


The cubic equation, x³-2x-5=0, is a depressed cubic and in this case 4p³+27q²>0. But the real root of equation comes out to be different, please see below.

1592807930198.png


The correct real solution is x≈2.0946 therefore the value x=2.4142 is not correct. Where am I going? Could you please help me?

[Moderator's note: Moved from a technical forum and thus no template.]
 
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Answers and Replies

  • #2
willem2
2,111
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I think you swapped p and q.
 
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  • #3
PainterGuy
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Thank you.

That was really silly!

1592813200902.png
 
  • #4
archaic
688
210
I'd say Prozac.
 
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  • #5
I'd say Prozac.

It just needs a hug :frown:

I think it's because all the other equations are calling him odd
 
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