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Mathematics 21 Online
OpenStudy (anonymous):

How many solutions does this equation have?

OpenStudy (anonymous):

9/x-5 + 4/x^2-3x-10 = 6/x+2

OpenStudy (anonymous):

I kind of know how to do this but not really

OpenStudy (anonymous):

I know I need a common denominator first

OpenStudy (anonymous):

I think there would be 2 solutions because the highest exponent tells you how many solutions there.

OpenStudy (anonymous):

which would be (x-5)(x+2)

OpenStudy (anonymous):

It does? I didnt know that.

OpenStudy (anonymous):

Yeah I learned that the exponents show how many solutions there are

OpenStudy (anonymous):

Ok then... lol

OpenStudy (anonymous):

Haha yeah i learned that from some earlier lesson I had in school a couple months ago.

OpenStudy (anonymous):

cool beans

OpenStudy (anonymous):

Is the following the problem expression?\[\frac{4}{x^2-3 x-10}+\frac{9}{x-5}=\frac{6}{x+2} \]

OpenStudy (anonymous):

YES

OpenStudy (anonymous):

Move the RHS to the LHS.\[\frac{4}{x^2-3 x-10}+\frac{9}{x-5}-\frac{6}{x+2}=0 \]Combine the fractions.\[\frac{52+3 x}{(-5+x) (2+x)}=0 \]The numerator has to be zero. There is only one solution,\[x=-\frac{52}{3} \]

OpenStudy (anonymous):

ok then 1 it is lol

OpenStudy (anonymous):

wait could you show me the last steps that lead to the final answer?

OpenStudy (anonymous):

you there???

OpenStudy (anonymous):

Yes.

OpenStudy (anonymous):

I used Mathematica and now I have to reverse engineer the answer.

OpenStudy (anonymous):

Ok.

OpenStudy (anonymous):

\[\frac{4}{x^2-3 x-10}+\frac{9(x+2)}{(x-5)(x+2)}-\frac{6(x-5)}{(x+2)(x-5)} \]\[\frac{4}{x^2-3 x-10}+\frac{9(x+2)}{\left(x^2-3 x-10\right)}-\frac{6(x-5)}{\left(x^2-3 x-10\right)} \]\[\frac{4+9(x+2)-6(x-5)}{x^2-3 x-10} \]\[\frac{(52+3 x)}{x^2-3 x-10} \]

OpenStudy (anonymous):

ok thats what i have. your final answer was different before. that is why i was asking.

OpenStudy (anonymous):

As it turns out the denominator can be factored.\[\frac{3 x+52}{x^2-3 x-10}=\frac{3 x+52}{(x-5) (x+2)} \]Mathematica frequently changes the order of terms and as a result it's expression forms "don't look right" and can be judged invalid by the casual observer. Takes a while to adjust to interpreting it's expressions, but then it becomes, second nature.

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