anonymous
  • anonymous
the algebraic expressions x-2 divided by x² -9is undefined when x is ..?
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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katieb
  • katieb
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anonymous
  • anonymous
It's undefined when the denominator is 0. This occurs when \[x^2-9=0 \rightarrow x=\pm 3\]
anonymous
  • anonymous
if the denominator is zero than wouldnt the answer be zero?
anonymous
  • anonymous
No, the denominator is zero for x-values such that \[x^2-9=0\] By what you're saying, if the answer is zero, x=0. But then the denominator would be \[0^2-9=-9\]which is fine. You can divide your expression by -9.

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More answers

anonymous
  • anonymous
\[\frac{x-2}{x^2-9}=\frac{something}{0}\]is undefined.
anonymous
  • anonymous
You have to find the x-values that make the denominator 0.
anonymous
  • anonymous
Is that clearer?
anonymous
  • anonymous
not really
anonymous
  • anonymous
Is it the 'undefined' thing, i.e. *why* you have to find x where x^2-9 = 0?
anonymous
  • anonymous
yea.. i dont understand that..
anonymous
  • anonymous
Okay. In division, you can't ever divide by 0. This is because, if we did it, we wouldn't actually end up with something that made sense. I'll give you a simple example.
anonymous
  • anonymous
ok
anonymous
  • anonymous
You're happy with\[\frac{6}{2}=3\] yeah?
anonymous
  • anonymous
yes
anonymous
  • anonymous
So if I then write,\[6=\left[ ? \right]\times 3\]what number would you put in there?
anonymous
  • anonymous
2
anonymous
  • anonymous
Right. Now,
anonymous
  • anonymous
if we imagine \[\frac{6}{0}=\left[ ? \right]\](i.e. *some* number)
anonymous
  • anonymous
we could write
anonymous
  • anonymous
\[6=0 \times \left[ ? \right]\]
anonymous
  • anonymous
What number would you put in now?
anonymous
  • anonymous
thats impossible
anonymous
  • anonymous
EXACTLY
anonymous
  • anonymous
We attempted to divide 6 by 0 and ended up with an IMPOSSIBILITY.
anonymous
  • anonymous
That's why division by zero is undefined.
anonymous
  • anonymous
Is that better?
anonymous
  • anonymous
This will happen no matter what you try to divide by zero.
anonymous
  • anonymous
yeahh
anonymous
  • anonymous
So that's why you have to find all the x-values that will end up making x^2-9 = 0 ... because everything falls apart there.
anonymous
  • anonymous
If x is 3 or -3, x^2-9 = 3^2-9 = 9 - 9 = 0 or x^2-9 = (-3)^2-9 = 9-9=0
anonymous
  • anonymous
\[\frac{x-2}{x^2-9}=\frac{3 -2}{3^2-9}=\frac{1}{0}\]when x=3
anonymous
  • anonymous
\[\frac{x-2}{x^2-9}=\frac{-3-2}{(-3)^2-9}=\frac{-5}{0}\]when x=-3.
anonymous
  • anonymous
oooooooooooooh alrighttt tanks
anonymous
  • anonymous
In both cases, you'll end up with the same rubbish you get with \[\frac{6}{0}\]
anonymous
  • anonymous
I think it's clicked now :)
anonymous
  • anonymous
Feel free to become a fan :P
anonymous
  • anonymous
:D
anonymous
  • anonymous
lol
anonymous
  • anonymous
Good luck with your algebra. Try and link it to numbers if you have trouble.
anonymous
  • anonymous
okeydokey

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