Math question

Scrapster

Diamond Member
Nov 27, 2000
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Here's the equation:

3y + y^2 = x^3 -x + c

c is constant.

Goal: solve for y.

What is the simplest way to solve for y?

Any ideas?

Scrapster
 

Unsickle

Golden Member
Feb 1, 2000
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quadratic equation Treat the right hand side as a constant C and then resubstitute once solved.
 

Scrapster

Diamond Member
Nov 27, 2000
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Unsickle,

Can you ellaborate more. Maybe work through the first few steps?

Scrapster
 

Scrapster

Diamond Member
Nov 27, 2000
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Woody,

Because I'm already done with half the problem. I'm stuck on this one part. It's the weekend so no tutors or instructors are around.

Scrapster
 

Mister T

Diamond Member
Feb 25, 2000
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y1 = (-3 + squareroot(4x^3-4x+4c+9))/2
y2 = (-3 - squareroot(4x^3-4x+4c+9))/2
 

Scrapster

Diamond Member
Nov 27, 2000
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Ok. I see the answer. But I don't understand how you got it.

Can someone please give me steps on how I can solve this problem?

Scrapster
 

Bluga

Banned
Nov 28, 2000
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Let (x^3 -x + c) = K ( K is constant)

so 3y + y^2 =K

==> y^2 +3y -K = 0

use equation y = [-b (+-) squareroot(b^2-4ac)] /2a

then substitue
 

Scrapster

Diamond Member
Nov 27, 2000
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I got it.

You guys were right and I just wasn't following well. I didn't think you could substitute (x^3 -x + c) as your quadratic constant. But once you do that, it's simple enough. I must have been sleeping that day in algebra class.

:)

Scrapster