sim. equ.

**lra11** · November 17th 2007, 06:26 AM

x^2+y^2=20
2y-x=0

simultaneous equations- started but doing something wrong.
please help

**Krizalid** · November 17th 2007, 06:29 AM

Originally Posted by lra11

x^2+y^2=20
2y-x=0

From the second equation $x=2y.$

Substitute that into the first equation, then solve for $y,$ after that you'll get the values for $x.$

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A related problem has been posted not long ago, let me find it and I'll edit my post. (Here is it. It's the same procedure.)

**red_dog** · November 17th 2007, 06:31 AM

From the second equation $x=2y$ .
Plug x in the first equation and you'll get
$x^2+4x^2=20\Leftrightarrow 5x^2=20\Leftrightarrow x^2=4\Leftrightarrow x=\pm 2$ .
Then $y=\pm 1$ .

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