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Mathematics 18 Online
OpenStudy (katherinesmith):

solve for x : equation inside

OpenStudy (katherinesmith):

\[\frac{ 3 }{ x + 2 } - \frac{ 1 }{ x } = \frac{ 1 }{ 5x }\]

OpenStudy (katherinesmith):

phi: this is my last question of the night. hahaha :)

OpenStudy (phi):

bring 1/5x to the left side find a common denominator

OpenStudy (katherinesmith):

i guess x is the common denominator?

OpenStudy (katherinesmith):

\[\frac{ 3 }{ x + 2 } - \frac{ 1 }{ x } - \frac{ 1 }{ 5x } = 0\]

OpenStudy (phi):

this is an equality, so not as tricky. another way to do this is multiply both sides (and all terms) by (x+2) and then by 5x (this "clears" the denominators) can you do that ?

OpenStudy (katherinesmith):

how would that clear the middle denominator?

OpenStudy (phi):

one step at at time. what do you get if you multiply all terms and both sides of the equation by (x+2) ?

OpenStudy (katherinesmith):

i have no idea.

OpenStudy (katherinesmith):

if you show me what it looks like when you multiply all the terms by (x + 2) i will do it and then try it myself with 5x

OpenStudy (phi):

just write (x+2) next to each term

OpenStudy (phi):

and remember you can simplify (x+2)/(x+2) to 1

OpenStudy (katherinesmith):

\[3 - \frac{ 1 }{ x ( x + 2) } - \frac{ 1 }{ 5x ( x + 2) } = (x + 2)\]

OpenStudy (katherinesmith):

actually its all equal to 0. dumb error in my fault

OpenStudy (phi):

yes, and you should by multiplying by (x+2). that means (x+2) goes in the "top" you divided by (x+2) (except for the first term, which you did correctly)

OpenStudy (katherinesmith):

\[3 - \frac{ x + 2 }{ x } - \frac{ x + 2 }{ 5x } = 0\]

OpenStudy (phi):

now multiply all terms, both sides by 5x. write 5x (in the top) next to each term

OpenStudy (katherinesmith):

\[3(5x) - \frac{ 5x ( x + 2) }{ x } - 1 = 0\]

OpenStudy (phi):

the last term is not -1. just put 5x next to the last term.

OpenStudy (katherinesmith):

my mistake. \[3(5x) - \frac{ 5x ( x + 2 }{ x } + 5x = 0\]

OpenStudy (katherinesmith):

is that right?

OpenStudy (phi):

5x times the last term. not just 5x

OpenStudy (katherinesmith):

\[3 ( 5x) - \frac{ 5x ( x + 2) }{ x } - \frac{ 5x }{ 5x} = 0 \]

OpenStudy (katherinesmith):

???

OpenStudy (phi):

\[ 3(5x) - \frac{ 5x(x + 2) }{ x } - \frac{ 5x(x + 2) }{ 5x } = 0(5x) \] now simplify. If you have the samething in the top and bottom, you can cancel them

OpenStudy (katherinesmith):

what do i do with \[\frac{ 5x ( x + 2) }{ x }\]

OpenStudy (phi):

the x in the top and bottom cancel, because x/x = 1

OpenStudy (katherinesmith):

so then i get 10x?

OpenStudy (katherinesmith):

\[15x - 10x - x + 2 = 0\]

OpenStudy (phi):

15x is ok \[ 3(5x) - \frac{ 5\cancel{x}(x + 2) }{ \cancel{x} } - \frac{ \cancel{5x}(x + 2) }{ \cancel{5x} } = 0(5x) \\ 15x - 5(x+2) -(x+2) = 0 \] can you finish ?

OpenStudy (katherinesmith):

yes

OpenStudy (katherinesmith):

9x = -12

OpenStudy (katherinesmith):

x = -12/9

OpenStudy (katherinesmith):

correct?

OpenStudy (katherinesmith):

actually x = 12/9

OpenStudy (phi):

what do you get when you distribute the -5 in -5(x+2) ? you should get -5 times each term

OpenStudy (katherinesmith):

yeah, -5x + -10

OpenStudy (katherinesmith):

15x - 5x - 10 - x - 2 = 0 9x - 12 = 0 9x = 12 x = 12/9

OpenStudy (phi):

you can simplify. top and bottom can be divided by 3

OpenStudy (katherinesmith):

x = 4/3

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