# Thread: How to make x the subject

1. ## How to make x the subject

Hi guys.

Stuck with this question...

P = [mx( x +a)] / C

Express x in terms of m, P and C and a

Looks relatively easy but is an impossible task for me to solve it. =(

Greatly Appreciate your help guys !

Thanks

2. Originally Posted by liukawa
Hi guys.

Stuck with this question...

P = [mx( x +a)] / C

Express x in terms of m, P and C and a

Looks relatively easy but is an impossible task for me to solve it. =(

Greatly Appreciate your help guys !

Thanks

3. Erm.

Can you give me more Hint pls.

I just simply cant make x an isolated variable by itself.

It has to get stuck with one of the variables.

4. Right after you multiplied each side by C (and divided by m if wanted), expand the right-hand side, what do you recognize ? Do you know the quadratic formula ?

5. Originally Posted by liukawa
Erm.

Can you give me more Hint pls.

I just simply cant make x an isolated variable by itself.

It has to get stuck with one of the variables.
Have you learned the quadratic equation?

6. Firstly expand it. This will help in solving it.

$\displaystyle P = \dfrac{mx( x +a)}{C}$

$\displaystyle P = \dfrac{mx^2 + mxa}{C}$

$\displaystyle PC = mx^2 + mxa$

$\displaystyle 0 = mx^2 + mxa - PC$

Now put the values into the quadratic formula to get x = ...

7. Originally Posted by Educated
Firstly expand it. This will help in solving it.

$\displaystyle P = \dfrac{mx( x +a)}{C}$

$\displaystyle P = \dfrac{mx^2 + mxa}{C}$

$\displaystyle PC = mx^2 + mxa$

$\displaystyle 0 = mx^2 + mxa - PC$

Now put the values into the quadratic formula to get x = ...
Thanks alot !

i get it now

By using the formula, i am able to get x =... !!

Thanks !