X-2=10

X(SQAURED)+Y(SQAURED)=20

I cant seem to get the formula to work...keeps on coming out uneven!!!

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- Feb 25th 2008, 09:40 AMENNOqaudratic eqautions
X-2=10

X(SQAURED)+Y(SQAURED)=20

I cant seem to get the formula to work...keeps on coming out uneven!!! - Feb 25th 2008, 09:43 AMJhevon
- Feb 25th 2008, 09:48 AMENNO
- Feb 25th 2008, 09:51 AMJhevon
ok. i think you need to provide more info. because i don't see what you want to do here. it seems you want to solve the equations simultaneously, but then the solution for x is given in the first equation which makes the problem trivial. simply substitute x = 12 into the second equation to solve for y. the problem is stupid, unless i am misinterpreting the directions and/or you made a typo

- Feb 25th 2008, 09:55 AMENNO
- Feb 25th 2008, 09:59 AMJhevon
- Feb 25th 2008, 10:02 AMENNO
- Feb 25th 2008, 10:08 AMJhevon
ok, we have:

$\displaystyle x - 2y = 10$ .................(1)

$\displaystyle x^2 + y^2 = 20$ ...........(2)

From (1), $\displaystyle x = 10 + 2y$, plug this into (2), we get:

$\displaystyle (10 + 2y)^2 + y^2 = 20$

$\displaystyle \Rightarrow 100 + 40y + 4y^2 + y^2 = 20$

$\displaystyle \Rightarrow 5y^2 + 40y + 80 = 0$

$\displaystyle \Rightarrow y^2 + 8y + 16 = 0$

this is a perfect square, we don't even need the quadratic formula here

$\displaystyle \Rightarrow (y + 4)^2 = 0$

$\displaystyle \Rightarrow y = -4$

now continue - Feb 25th 2008, 10:28 AMENNO
- Feb 25th 2008, 07:53 PMJhevon
- Feb 25th 2008, 08:01 PMmr fantastic