# Isolating x?

• Sep 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?
• Sep 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 $\displaystyle y=\frac{-4+2x}{5+x}$ then it is possible to write $\displaystyle x$ as a function of $\displaystyle y$.

Is that the same as your question?
• Sep 23rd 2011, 12:43 PM
Dmiller93
Re: Isolating x?
Yes, it's the same.
• Sep 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.
• Sep 23rd 2011, 12:47 PM
Dmiller93
Re: Isolating x?
Sorry, could you clarify? I'm not quite sure how to go about doing that.
• Sep 23rd 2011, 01:53 PM
Siron
Re: Isolating x?
Rewrite:
$\displaystyle y=\frac{-4+2x}{5+x}$
$\displaystyle \Leftrightarrow y(5+x)=-4+2x$
$\displaystyle \Leftrightarrow 5y+yx=-4+2x$
$\displaystyle \Leftrightarrow 2x-yx=5y+4$
$\displaystyle \Leftrightarrow x(2-y)=5y+4$
$\displaystyle \Leftrightarrow x=...$