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Mathematics 22 Online
OpenStudy (dobby1):

@phi Question is below

OpenStudy (dobby1):

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OpenStudy (dobby1):

can you help me with this I have no idea what to do

OpenStudy (phi):

is the problem \[ \frac{ \frac{4}{(x+3)}}{\frac{1}{x}+3}\]?

OpenStudy (dobby1):

yes

OpenStudy (phi):

I would first add 1/x + 3 to do that, use a common denominator of x. that means multiply the 3 (which is 3/1) by x/x then add the tops can you do that ?

OpenStudy (dobby1):

I think so so multiply the bottoms of 3/1 and x/x then add 3+x ?

OpenStudy (phi):

what do you get ?

OpenStudy (dobby1):

3+x/x right?

OpenStudy (phi):

3 * x/x means 3/1 * x/x which means 3*x (top * top) divided by 1*x (bottom*botom) in other words \[ 3 \cdot \frac{x}{x} = \frac{3x}{x} \] now add the fractions \[ \frac{1}{x} + \frac{3x}{x} \] what do you get ?

OpenStudy (phi):

to add fractions with the same bottom, add the tops, and keep the bottom as it was.

OpenStudy (dobby1):

1+3x/x Right?

OpenStudy (phi):

yes. so now your problem is \[ \frac{ \frac{4}{(x+3)}}{\frac{3x+1}{x}}\] we can now flip the bottom fraction, and multiply (instead of divide) follow ?

OpenStudy (phi):

what is the inverse of (3x+1)/x in other words, can you write down the "flip" of that fraction ?

OpenStudy (dobby1):

uhm you can make the bottom fraction x/(3x+1) which would make it 4/(x+3)*x/(3x+1) right?

OpenStudy (dobby1):

you there?

OpenStudy (dobby1):

@phi

OpenStudy (phi):

yes, you are correct. you get \[ \frac{4}{x+3} \cdot \frac{x}{3x+1} = \frac{4x}{(x+3)(3x+1)} \] which you may (depends on how the answers are shown) multiply out to \[ \frac{4x}{3x^2+10x+3} \]

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