Integral Calculus Antiderivative Question

xskull
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Homework Statement



Find the antiderivative of:

\int \frac{dx}{x^3 - 2x^2 + 4x - 18}

Homework Equations



This was asked in my Calculus II class right after we finished dealing with Solving for
Integrals using Partial Fractioning.

The Attempt at a Solution



This is really more of an algebra question as all I need to know are the factors
of the denominator to be able to start applying Partial Fractions.

I've been browsing the internet for ways to factor this. I read about the http://en.wikipedia.org/wiki/Rational_root_theorem"
and used Synthetic Division for every root that the theorem gave me, but to no avail.

I also tried simplifying the equation, although it didn't looked simplified, but letting
x = y + 2/3
then letting
y = z - (8/3)/9z
to produce the equation: 729z^6 - 11610z^3 - 512
Doing the above doesn't help me much, though.

Someone advised me to apply Numerical Integration, I don't know why since we haven't discussed about it yet.

I'm starting to wonder if this can be solved. Please advise.
 
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xskull said:

Homework Statement



Find the antiderivative of:

\int \frac{dx}{x^3 - 2x^2 + 4x - 18}

Homework Equations



This was asked in my Calculus II class right after we finished dealing with Solving for
Integrals using Partial Fractioning.

The Attempt at a Solution



This is really more of an algebra question as all I need to know are the factors
of the denominator to be able to start applying Partial Fractions.

I've been browsing the internet for ways to factor this. I read about the http://en.wikipedia.org/wiki/Rational_root_theorem"
and used Synthetic Division for every root that the theorem gave me, but to no avail.

I also tried simplifying the equation, although it didn't looked simplified, but letting
x = y + 2/3
then letting
y = z - (8/3)/9z
to produce the equation: 729z^6 - 11610z^3 - 512
Doing the above doesn't help me much, though.

Someone advised me to apply Numerical Integration, I don't know why since we haven't discussed about it yet.

I'm starting to wonder if this can be solved. Please advise.

I'm curious, what compelled you to make those substitutions for x,y,z? And now let w=z3...
 
Last edited by a moderator:
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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