Changing the subject involving division

**Meggomumsie** · September 28th 2009, 01:16 AM

What is my first move please?

$y=\frac{5+x}{1-x}$

**Grandad** · September 28th 2009, 01:33 AM

Hello Meggomumsie

Originally Posted by Meggomumsie

What is my first move please?

$y=\frac{5+x}{1-x}$

Get rid of fractions - always a good move in handling any equation. So, multiply both sides by $(1-x)$ :

$y(1-x) = 5+x$

Then:

Remove brackets on the LHS

Collect terms in $x$ on one side only; everything else on the other side

Take out a common factor of $x$ (by writing $x$ outside a bracket with the other bits inside)

Divide both sides by the resulting bracket to make $x$ the subject.

Can you complete it now?

Grandad

**Meggomumsie** · September 28th 2009, 05:21 AM

Thank you for your answer. I would still be pondering without your prompts as I have not been taught to factorise in the middle of changing the subject of a formula. So here is my attempt.

$y=\frac{5+x}{1-x}$

y(1 - x) = 5 + x

y - xy = 5 + x

y -5 = x + xy

y - 5 = x(1 + y)

$\frac{y-5}{y+1}=x$

It's great to be learning, thank you all ~ Marilyn

**Grandad** · September 28th 2009, 07:18 AM

Well done! Looks good to me.

Grandad

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