# Thread: Changing the subject question help!

1. ## Changing the subject question help!

I need to make a the subject, but i keep ending up with 0 a's. Can someone please give a step by step to how they did it if they know the answer.

And thankyou to anyone in advanced.

b = (a + x) / (a + c)

edit: the right side is meant to be a fraction, but the best way i can think of writing is is with a '/'.

2. Originally Posted by nugiboy
I need to make a the subject, but i keep ending up with 0 a's. Can someone please give a step by step to how they did it if they know the answer.

And thankyou to anyone in advanced.

b = (a + x) / (a + c)

edit: the right side is meant to be a fraction, but the best way i can think of writing is is with a '/'.
$b = \frac{a + x}{a + c}$

$b(a + c) = a + x$

$ab + bc = a + x$

$ab - a = x - bc$

$a(b - 1) = x - bc$

$a = \frac{x - bc}{b - 1}$

Of course, we need to recall that $a \neq -c$ else the original expression can't exist.

-Dan

3. Originally Posted by nugiboy
I need to make a the subject, but i keep ending up with 0 a's. Can someone please give a step by step to how they did it if they know the answer.

And thankyou to anyone in advanced.

b = (a + x) / (a + c)

edit: the right side is meant to be a fraction, but the best way i can think of writing is is with a '/'.
$
b=\frac{a+x}{a+c}
$

So:

$
(a+c)b=a+x
$

or:

$
(b-1)a=x-cb
$

so:

$
a=\frac{x-cb}{b-1}
$

RonL