3a, add +b and then cube the entire thing?

  • #1
A quick question... what is the resultant expression if you multiply the cubic formula by 3a, add +b and then cube the entire thing?

Much appreciated
 

Answers and Replies

  • #2
berkeman
Mentor
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A quick question... what is the resultant expression if you multiply the cubic formula by 3a, add +b and then cube the entire thing?

Much appreciated
Pi.

Cool problem. Thanks.
 
  • #3
chiro
Science Advisor
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Pi.

Cool problem. Thanks.
Aside from delicious pi, have you tried just writing the equation of a cubic polynomial down and then doing your operations using normal algebra?
 
  • #4
HallsofIvy
Science Advisor
Homework Helper
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To clarify, what do you mean by "the cubic formula"? chiro seems to think you mean just a cubic polynomial. Is that correct?
 
  • #5
I'm trying to rewrite the cubic formula (the general solution for the roots of a cubic polynomial into the form (3ax +b)^3 = ...

Where normally given a cubic polynomial equation

ax^3 + bx^2 + cx + d = 0

The answer can be found by making the substitution:

a = b/a

b = c/a

c = d/a

and then the formula is in this link:

http://planetmath.org/encyclopedia/CubicFormula.html [Broken]
 
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