anonymous
  • anonymous
-4sqrt(x+9)=20 can anyone help?
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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katieb
  • katieb
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anonymous
  • anonymous
\[-4 \sqrt{(x+9)} = 20\] Like this? At what part are you getting stuck?
anonymous
  • anonymous
well i get x=16 but when i try to see if its true i get -20=20
anonymous
  • anonymous
and yes like that

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anonymous
  • anonymous
Yeah, with that -4 outside the square root, I think it's undefined.
anonymous
  • anonymous
yeah your probably right. extraneous solution?
anonymous
  • anonymous
If we defined \(y\) as \(\sqrt{(x+9)}\), we would get \(-4y = 20\), with \(y = -5\), and there is no way \(\sqrt{(x+9)} = -5\)
anonymous
  • anonymous
hmmm i dont know. but when we divide -4 we get \[\sqrt{x+9}=-5\]
anonymous
  • anonymous
\(\large{\sqrt{-x} = i \sqrt{x}}\) right?
anonymous
  • anonymous
yeah
anonymous
  • anonymous
Okay, can we use that somehow?
anonymous
  • anonymous
Oh wait... We can square both sides, right?
anonymous
  • anonymous
hmmm yeah
anonymous
  • anonymous
and we get x+9=25 because -5x-5=25
anonymous
  • anonymous
Right, so you were right with 16; it is an extraneous root.
anonymous
  • anonymous
yeah it looks like that then and thanks man
anonymous
  • anonymous
Hey, no problem. :)

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