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Mathematics 16 Online
OpenStudy (anonymous):

I need help please!!!

OpenStudy (anonymous):

x+10/x+3 +90/x^2-30=0

OpenStudy (anonymous):

\[\frac{ x+10 }{ x+3 }+\frac{ 90 }{ x^2-30 }=0\]

OpenStudy (mathstudent55):

Are you sure you copied the problem correctly? I especially mean the second denominator?

OpenStudy (anonymous):

90/x^2-25

OpenStudy (mathstudent55):

I don't understand your answer. I asked you about a problem and you write a completely different problem.

OpenStudy (anonymous):

sorry I am having trouble with the equation editor...the second denominator was wrong, that's why I corrected it.

OpenStudy (mathstudent55):

Oh, I get it. You mean the correct second denominator is x^2 - 25?

OpenStudy (anonymous):

yes

OpenStudy (mathstudent55):

Ok, let's do it.

OpenStudy (anonymous):

Okay

OpenStudy (mathstudent55):

The first step is to factor all denominators. Obviously, the left denominator has nothing to factor. Can you factor the right denominator?

OpenStudy (mathstudent55):

Before we continue, can you please check the rest of the problem is correct? Is this it? \(\large \dfrac{ x+10 }{ x+3 }+\dfrac{ 90 }{ x^2-25 }=0\)

OpenStudy (anonymous):

yes

OpenStudy (mathstudent55):

Ok. Remember you changed the second denominator to \(x^2 - 25\) This is the difference of two squares which factors like this: \(a^2 - b^2 = (a + b)(a - b) \)

OpenStudy (anonymous):

oops.....(x+5)(x-5)=0

OpenStudy (mathstudent55):

Ok. We now have this: \(\large \dfrac{ x+10 }{ x+3 }+\dfrac{ 90 }{ (x+5)(x-5) }=0\)

OpenStudy (anonymous):

yes

OpenStudy (mathstudent55):

Once again, you are positive that the first fraction is correct, right? The left denominator is definitely x + 3?

OpenStudy (anonymous):

yes

OpenStudy (mathstudent55):

Ok. The next step is to multiply both sides by the LCD of the denominators.

OpenStudy (mathstudent55):

There are three different factors in the denominators, so the LCD is the product of all three factors.

OpenStudy (mathstudent55):

LCD = (x + 3)(x + 5)(x - 5)

OpenStudy (mathstudent55):

Now we multiply both sides by the LCD. \( (x + 3)(x + 5)(x - 5)\dfrac{ x+10 }{ x+3 }+(x + 3)(x + 5)(x - 5)\dfrac{ 90 }{ (x+5)(x-5)}=\) \(=(x + 3)(x + 5)(x - 5) \times 0\)

OpenStudy (mathstudent55):

The right side is zero since we are multiplying by zero. \( \cancel{(x + 3)}(x + 5)(x - 5)\dfrac{ x+10 }{\cancel{ x+3} }+(x + 3)\cancel{(x + 5)}(\cancel{x - 5})\dfrac{ 90 }{ (\cancel{x+5})(\cancel{x-5})}= 0\) \( (x + 5)(x - 5)(x+10)+ (x + 3) \times 90 = 0\) \( (x + 5)(x - 5)(x+10)+ 90(x + 3) = 0\) Now you need to multiply out the three trinomials on the left and 90(x + 3), and combine like terms. You will end up with a third degree polynomial which needs perhaps trial and error to solve. What kind of math are you learning?

OpenStudy (anonymous):

College Algebra

OpenStudy (mathstudent55):

Have you dealt with solutions to third degree polynomials or only quadratic equations?

OpenStudy (anonymous):

Only quadratic equation..this since to be hard

OpenStudy (mathstudent55):

If this problem is in a section that deals with quadratic equations, then there must be a mistake in the problem.

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