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#1 2008-02-17 11:51:52
- freddogtgj
- Member
- Registered: 2006-12-02
- Posts: 54
Make y as the sunject...
I need to make y as the subject of the following question:
Any suggestions?
Thanks in advance!
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#2 2008-02-17 12:22:40
- mathsyperson
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- Registered: 2005-06-22
- Posts: 4,900
Re: Make y as the sunject...
Completing the square looks like your best option. The quadratic formula works too, but it's a nice one to complete the square with so I'd do it that way.
It looks like y's going to be complex for nearly all values of x though.
Why did the vector cross the road?
It wanted to be normal.
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#3 2008-02-17 12:25:14
- Daniel123
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- Registered: 2007-05-23
- Posts: 663
Re: Make y as the sunject...
I get
by completing the square.. not sure if that's allowed. :SEDIT: Ahh you beat me to it. Now I know it's OK I'll show my working:
Last edited by Daniel123 (2008-02-17 12:29:37)
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#4 2008-02-17 13:07:14
- mathsyperson
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- Registered: 2005-06-22
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Re: Make y as the sunject...
Don't forget the ± in front of the root. [/picky]
Why did the vector cross the road?
It wanted to be normal.
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#5 2008-02-17 13:12:26
- Daniel123
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- Registered: 2007-05-23
- Posts: 663
Re: Make y as the sunject...
It's late.. let me off 
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#6 2008-02-18 10:48:19
- freddogtgj
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- Registered: 2006-12-02
- Posts: 54
Re: Make y as the sunject...
of course...we have an equation of a circle in there as well!
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#7 2008-02-18 12:09:23
- mathsyperson
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- Registered: 2005-06-22
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Re: Make y as the sunject...
Well, sort of. The equation works out as x² + (y+2)² = 0, so you get a circle centred at (0,-2) with radius 0.
But as the radius is 0, it's really just a point.
Why did the vector cross the road?
It wanted to be normal.
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