Need a strategy for inverting a function

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Discussion Overview

The discussion revolves around strategies for inverting a function defined by the equation x = -K1 * y * √(K2 - y), where K1 and K2 are constants. Participants explore methods for solving for y, including algebraic manipulations and the implications of different solutions.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant expresses difficulty in solving for y and seeks strategies for inverting the function.
  • Another participant suggests squaring both sides of the equation, leading to a cubic equation in y, and notes that y=0 is an evident solution.
  • A different participant questions the validity of y=0 as a solution and references an external resource for solving cubic equations.
  • Further discussion includes a participant sharing a general form for the solutions of cubic equations and speculating on which solutions avoid imaginary numbers.

Areas of Agreement / Disagreement

The discussion contains multiple competing views regarding the approach to solving the equation and the nature of the solutions, particularly concerning the solution y=0 and the implications of different forms of the cubic equation.

Contextual Notes

Participants have not fully resolved the implications of the cubic equation or the conditions under which certain solutions are valid, leaving some assumptions and mathematical steps unaddressed.

MCarroll
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I can't solve for y from:

x = - [tex]K_{1}[/tex]* y *[tex]\sqrt{K_{2}-y}[/tex]

where K(1) and K(2) are constants.

I am pretty sure as a younger man I was taught how to do this but I can't remember the strategies I can/should use. Any thougths would be very appreciated.
 
Last edited:
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Square both sides and you get a cubic in y, out of which the solution y=0 is evident, so you've only got a simple quadratic to solve.
 
Thanks, and genneth I'm not one to talk!

Shooting Star, It looks from the page you sent that the general form is:

y = 3f/[-e+(e3-27f2)1/3],
y = 3f/[-e+(e3-27f2)1/3(-1+sqrt[-3])/2],
y = 3f/[-e+(e3-27f2)1/3(-1-sqrt[-3])/2].

so only the first of these avoids i, right?
 

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