Simplify the rational expression. State any restrictions on the variable.
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OpenStudy (anonymous):
\[\frac{ n^4-10n^2+24 }{ n^4-9^2+18 }\]
OpenStudy (math&ing001):
First lets find the restrictions. For that we solve for n : n^4 - 9^2 + 18 = 0
OpenStudy (anonymous):
Than what? @math&ing001
OpenStudy (anonymous):
OpenStudy (anonymous):
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OpenStudy (anonymous):
OpenStudy (anonymous):
OpenStudy (anonymous):
@Hero
OpenStudy (anonymous):
@satellite73
hero (hero):
Let \(n^2 = y\) then try simplifying the expression.
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OpenStudy (anonymous):
Please help me I know its \[\frac{ n^2-4 }{ n^2-3}\] but i dont know the other half for my answer, so it's between A-C for the answer
OpenStudy (anonymous):
(n+2)(n−2)(n2−6)
(n2−3)(n2−6)
hero (hero):
How do you know it's \(\dfrac{n^2 - 4}{n^2 - 3}\)?
OpenStudy (anonymous):
(n+2)(n−2)(n2−6)
(n2−3)(n2−6)
hero (hero):
Multiply it back out to see if what you get matches the original expression.
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hero (hero):
Also the original expression you posted likely has a typo in it somewhere.
OpenStudy (anonymous):
How do i do that?
OpenStudy (anonymous):
@timo86m
OpenStudy (anonymous):
@Astrophysics
OpenStudy (anonymous):
@Michele_Laino can you please help me finish my math problem?
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OpenStudy (anonymous):
@mathmate
OpenStudy (anonymous):
I just need help with the end of the problem. I think the answer is B though
OpenStudy (mathmate):
@EllenJaz17
Please confirm that the problem is indeed:
\(\Large \frac{ n^4-10n^2+24 }{ n^4-9\color{red}{n}^2+18 } \)
OpenStudy (anonymous):
yes
OpenStudy (anonymous):
Yes it is @mathmate
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OpenStudy (michele_laino):
hint:
we can factorize the denominator, using the same procedure for numerator, so
we can write this:
\[{n^4} - 9{n^2} + 18 = \left( {{n^2} - 6} \right)\left( {{n^2} - 3} \right)\]
OpenStudy (anonymous):
(n+2)(n−2)(n2−6)
(n2−3)(n2−6)
OpenStudy (anonymous):
\[\frac{ n^2-4 }{ n^2-3 }\]
OpenStudy (michele_laino):
yes!
OpenStudy (anonymous):
I know thats the answer to the first half but i need to find out the second half
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OpenStudy (anonymous):
OpenStudy (anonymous):
OpenStudy (anonymous):
OpenStudy (anonymous):
OpenStudy (michele_laino):
the denominator is equal to zero when these two conditions hold:
\[\begin{gathered}
{n^2} - 6 = 0 \hfill \\
\hfill \\
{n^2} - 3 = 0 \hfill \\
\end{gathered} \]
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OpenStudy (michele_laino):
please remember, that we can not divide by zero
OpenStudy (anonymous):
correct
OpenStudy (michele_laino):
please solve those quadratic equations for n, what do you get?
OpenStudy (anonymous):
6 and 3?
OpenStudy (michele_laino):
are you sure?
we have 6^2= 36, and 3^2=9
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OpenStudy (anonymous):
No im not sure im just guessing
OpenStudy (michele_laino):
hint:
the solution to this equation:
\[{n^2} - k = 0\]
are:
\[n = \sqrt k ,\quad n = - \sqrt k \]
OpenStudy (michele_laino):
solutions*
OpenStudy (michele_laino):
since:
\[{\left( {\sqrt k } \right)^2} = {\left( { - \sqrt k } \right)^2} = {n^2}\]
OpenStudy (michele_laino):
being k a positive number or k=0
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OpenStudy (anonymous):
So is it answer B?
OpenStudy (michele_laino):
no, I don't think so, sorry!
OpenStudy (anonymous):
OpenStudy (michele_laino):
hint:
what are the solution of this equation:
\[{n^2} - 3 = 0\] ?
OpenStudy (anonymous):
So that only leaves A & C correct? because D isn't \[\frac{ n^2-4 }{ n^2-3 }\]
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OpenStudy (michele_laino):
solutions*
OpenStudy (anonymous):
\[n^{2}=3?\]
OpenStudy (michele_laino):
yes! and what is n=...?
OpenStudy (anonymous):
\[n \neq \pm \sqrt{6}\pm \sqrt{3}?\]
OpenStudy (michele_laino):
from this equation:
\[{n^2} - 3 = 0\]
I get
\[n = \pm \sqrt 3 \]
am I right?
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OpenStudy (anonymous):
yes
OpenStudy (michele_laino):
ok! so we have to exclude those 2 values, since when:
\[n = \pm \sqrt 3 \]
the denominator is zero
Now do the same with the equation:
\[{n^2} - 6 = 0\]
OpenStudy (anonymous):
\[n=\pm \sqrt{6}\]
OpenStudy (michele_laino):
perfect, we have to exclude those values too, since when:
\[n = \pm \sqrt 6 \]
the denominator is zero.
So what is the right option?
OpenStudy (anonymous):
A
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OpenStudy (michele_laino):
that's right! :)
OpenStudy (anonymous):
Thank you so much for teaching me how to get to the answer!