I am trying to rearrange this equation

Q=0.098[(D^4-d^4)/D]

For D=

I have spent to hours factoriseing, swapping sides, etc. but im getting nowhere.

Please Help

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- Apr 26th 2012, 07:02 AMgwood311Re-arrange equation for D
I am trying to rearrange this equation

Q=0.098[(D^4-d^4)/D]

For D=

I have spent to hours factoriseing, swapping sides, etc. but im getting nowhere.

Please Help - Apr 26th 2012, 07:10 AMprincepsRe: Re-arrange equation for D
- Apr 26th 2012, 08:00 AMgwood311Re: Re-arrange equation for D
What does "WA" mean

- Apr 26th 2012, 05:33 PMHallsofIvyRe: Re-arrange equation for D
So "D" and "d" are different? "D" is the value you want to determine and "d" is some given value?

$\displaystyle Q= 0.098\frac{D^4- d^4}{D}$

Multiply both sides by D:

$\displaystyle QD= 0.098(D^4- d^4)$

Do the multiplication on the right and subtract QD from both sides:

$\displaystyle 0.098D^4- QD- d^4= 0$

Now that is a fourth degree equation. There is a "formula" for solving general fourth degree equations but it is very complicated:

Quartic function - Wikipedia, the free encyclopedia - Apr 26th 2012, 05:45 PMskeeterRe: Re-arrange equation for D
- Apr 26th 2012, 10:03 PMkalwinRe: Re-arrange equation for D
Hi friends, Algebra is really very complicated, even i was facing such problem in Algebra. You guys are really working hard and helping each by solving each other Algebra queries. You can also go for online Algebra Tutor.

- Apr 26th 2012, 11:37 PMgwood311Re: Re-arrange equation for D
Thanks for help guys. Didn't realise the WA was a hyperlink, thanks.

After looking into the 4th degree equation I found the equation must be in the format:

ax^4 + bx^2 + c=0

In my equation the middle part is not squared so I cannot solve the equation.

I am beginning the think the equation cannot be rearranged simply for D and the only answer for it is on WA provided by princeps - Apr 27th 2012, 01:32 AMWilmerRe: Re-arrange equation for D
- Apr 27th 2012, 02:18 AMgwood311Re: Re-arrange equation for D
That equation is a quadratic; let u = x^2, then au^2 + bu + c = 0.

My equation which is; 0.098D^4 - QD - 0.098d^4 = 0

Letting u=D^2 in this case will not work. - Apr 27th 2012, 07:41 AMWilmerRe: Re-arrange equation for D