How do I Expand a Cubic Problem?

[Grove1996]

Homework Statement

Hey

I have a question that I have to do that involves expanding a cubic. It is given in the form y = , once it is found I have to square it and then substitute it into a formula to find the area. All I need help with is the expansion than after that it's quite easy.

Homework Equations

Sorry I don't know how to use the options here to create formulas etc. But I hope the following link works.

https://www.physicsforums.com/attachment.php?attachmentid=58828&stc=1&d=1368927170

This is the equation that I need to expand.

The Attempt at a Solution

I know how to expand a cubic already, it's not that difficult. The problem is with the +2 at the end of the equation. Do I ignore it, expand the brackets and add it on at the end?

 

[rock.freak667]

Hi Grove1996,

Usually you would do the operations in the brackets first and then simplify after. So yes you would need to add the 2 to the constant from the cubic expansion

So when do any expansion, you would sum up all the x's and constants and so on.

e.g. (x+1)²+4 = (x+1)(x+1) + 4 = x² + x +x +1 +4 = x² + 2x + 5

 

[Grove1996]

Hi Grove1996,

Usually you would do the operations in the brackets first and then simplify after. So yes you would need to add the 2 to the constant from the cubic expansion

So when do any expansion, you would sum up all the x's and constants and so on.

e.g. (x+1)²+4 = (x+1)(x+1) + 4 = x² + x +x +1 +4 = x² + 2x + 5

Thank you :)

 

[Grove1996]

Just attempted the solution and here it is

https://www.physicsforums.com/attachment.php?attachmentid=58830&stc=1&d=1368928386

Is that correct?

 

[Cogswell]

Yes, it is correct, but you can further simplify it:

For example:
$-1.5 x^4 -3 x^4 = (-1.5 - 3)x^4 = -4.5x^4$

 

[SammyS]

Yes, it is correct, but you can further simplify it:

In other words: Combine like terms.