# Expanding a cubic problem

1. May 18, 2013

### Grove1996

1. The problem statement, all variables and given/known data

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.

2. Relevant 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.

3. 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?

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2. May 18, 2013

### 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

3. May 18, 2013

### Grove1996

Thank you :)

4. May 18, 2013

### Grove1996

#### Attached Files:

• ###### Problem.PNG
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5. May 18, 2013

### Cogswell

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

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

6. May 19, 2013

### SammyS

Staff Emeritus
In other words: Combine like terms.