Isolating x?

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September 23rd 2011, 12:38 PM
Dmiller93

Isolating x?

Is it possible to isolate x in the following: f(x) = -4 +2x / 5 + x? If so, how?
September 23rd 2011, 12:42 PM
Plato

Re: Isolating x?

Quote:

Originally Posted by Dmiller93

Is it possible to isolate x in the following: f(x) = -4 +2x / 5 + x? If so, how?

Not sure of the question??
If $y=\frac{-4+2x}{5+x}$ then it is possible to write $x$ as a function of $y$ .

Is that the same as your question?
September 23rd 2011, 12:43 PM
Dmiller93

Re: Isolating x?

Yes, it's the same.
September 23rd 2011, 12:45 PM
Plato

Re: Isolating x?

Quote:

Originally Posted by Dmiller93

Yes, it's the same.

From reply #2, just solve that equation for x in terms of y.
September 23rd 2011, 12:47 PM
Dmiller93

Re: Isolating x?

Sorry, could you clarify? I'm not quite sure how to go about doing that.
September 23rd 2011, 01:53 PM
Siron

Re: Isolating x?

Rewrite:
$y=\frac{-4+2x}{5+x}$
$\Leftrightarrow y(5+x)=-4+2x$
$\Leftrightarrow 5y+yx=-4+2x$
$\Leftrightarrow 2x-yx=5y+4$
$\Leftrightarrow x(2-y)=5y+4$
$\Leftrightarrow x=...$

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