# radical equation problem help

• August 13th 2011, 04:42 PM
mathmathmathmathmathmathm
radical equation problem help
$\sqrt{x+7}-2\sqrt{x}=-2$

$\left(\sqrt{x+7}\right)^2=\left(-2+2\sqrt{x}\right)^2$

$x+7=4-8\sqrt{x}+4x$

$\left(-3x-3\right)^2=\left(-8\sqrt{x}\right)^2$

$9x^2+18x+9=64x$

$9x^2-46x+9=0$

iam lost after that, reviewed it and cant figure out what went wrong, the answer is 9
• August 13th 2011, 04:57 PM
skeeter
Re: radical equation problem help
Quote:

Originally Posted by mathmathmathmathmathmathm
$\sqrt{x+7}-2\sqrt{x}=-2$

$\left(\sqrt{x+7}\right)^2=\left(-2+2\sqrt{x}\right)^2$

$x+7=4-8\sqrt{x}+4x$

$\left(-3x-3\right)^2=\left(-8\sqrt{x}\right)^2$ this line ... should be (-3x+3)^2 on the left side

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