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Mathematics 25 Online
OpenStudy (anonymous):

Just wanted to check my answers if they are right. (See below)

OpenStudy (anonymous):

1.)\[\frac{ x-4 }{ x^2-3x-4 }\]

OpenStudy (anonymous):

My answer: \[\frac{ 1 }{ (x+1) }\]

OpenStudy (anonymous):

1 is correct

OpenStudy (anonymous):

Thanks! 2.) \[\frac{ x^3-8 }{ x-2 }\]

OpenStudy (anonymous):

My answer:\[(x+2)^2\]

OpenStudy (anonymous):

I think u can simplify more than that

OpenStudy (anonymous):

How would I simplify that?

OpenStudy (anonymous):

hold on

OpenStudy (anonymous):

something is wrong

OpenStudy (anonymous):

I don't think I factored the numerator right.

OpenStudy (anonymous):

start by putting the 8 into 2^3

OpenStudy (anonymous):

Okay. Then what?

OpenStudy (anonymous):

and use the difference of cubes which is \[a^3−b^3=(a−b)(a^2+ab+b^2)\]

OpenStudy (anonymous):

it will get you \[(x−2)(x^2+(x)(2)+2^2)\]

OpenStudy (anonymous):

Simplify 2^2 to 4 and regroup terms

OpenStudy (anonymous):

\[\frac{ (x−2)(x^2+2x+4) }{ x-2 }\]

OpenStudy (anonymous):

now just cancel the x-2

OpenStudy (anonymous):

did you get it?

OpenStudy (anonymous):

Ya I got it. Wasn't that the same answer I got?

OpenStudy (anonymous):

\[(x+2)^2\]

OpenStudy (anonymous):

It's different

OpenStudy (anonymous):

I wrote the same answer.

OpenStudy (anonymous):

\[x^2+2x +4 \neq (x+2)^2\]

OpenStudy (anonymous):

Ya sorry about that. Just noticed.

OpenStudy (anonymous):

I would have to use the quadratic formula for this right?

OpenStudy (zale101):

\(a^3-b^3=(x-a)(a^2+ab+b^2)\) \(x^3-2^3=(x-2)(x^2+2x+2^2)=x^2+2x+4\) \(\Large\frac{x^3-8}{x-2}=\frac{x^2-2^3}{x-2}=\frac{(x-2)(x^2+2x+4)}{x-2}\)

OpenStudy (zale101):

\(\Large =x^2+2x+4\)

OpenStudy (anonymous):

Ya I got that so far. Thanks!

OpenStudy (anonymous):

\[\frac{ -2\pm \sqrt{2^2-4(1)(4)} }{ 2(1) }\]\[\frac{ -2\pm \sqrt{4-16} }{ 2 }\]\[\frac{ -2\pm \sqrt{-12} }{ 2 }\]

OpenStudy (anonymous):

The answer is going to have an i?

OpenStudy (zale101):

Yes. That's why it cant be factored. If you get complex numbers when factoring, then the polynomial is irreducible. x^2+2x+4 is a prime polynomial.

OpenStudy (anonymous):

So I don't have to simplify that then? Do I just put x^2+2x+4?

OpenStudy (zale101):

Yes :)

OpenStudy (anonymous):

Alright thanks! 3.)\[\frac{ 5-x }{ x^2-25 }\]

OpenStudy (anonymous):

My answer:\[\frac{ -1 }{ x+5 }\]

OpenStudy (anonymous):

4.) \[\frac{ x^2-4x-32 }{ x^2-16 }\]

OpenStudy (alekos):

3 is correct

OpenStudy (anonymous):

My answer:\[\frac{ x-8 }{ x-4 }\]

OpenStudy (anonymous):

Thanks! What about #4?

OpenStudy (alekos):

yes. well done

OpenStudy (anonymous):

Thanks you guys!

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