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#1 2010-01-07 01:01:38
- henrybrice
- Member
- Registered: 2009-11-09
- Posts: 6
equation to the fourth power
I know how to find the solutions to a quadratic equation, but how can I find the answers to
(x^4) - (x^2) - 1 = 0?
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#2 2010-01-07 01:24:15
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: equation to the fourth power
Hi henrybrice;
Try the substitution y = x^2
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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#3 2010-01-07 03:25:48
- henrybrice
- Member
- Registered: 2009-11-09
- Posts: 6
Re: equation to the fourth power
But the answers I get are one positive and one negative, and x^2 cannot be negative...
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#4 2010-01-07 03:42:46
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: equation to the fourth power
Hi;
Not true, you can have an equation,
x^2 = - 5 then x equals -i √ 5 and i √ 5
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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#5 2010-01-07 04:21:54
- mathsyperson
- Moderator
- Registered: 2005-06-22
- Posts: 4,900
Re: equation to the fourth power
Or, if you're not interested in complex solutions, then you just state that there are only two.
In the same way that you could say that x^2 + 5 = 0 has no solutions.
Why did the vector cross the road?
It wanted to be normal.
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