# Thread: Rearrange to find X.

1. ## Rearrange to find X.

How do I rearrange this to find X?
X(A + 2B) = 10
I don't really get what I have to do to rearrange it.

2. Originally Posted by Aihem
How do I rearrange this to find X?
X(A + 2B) = 10
I don't really get what I have to do to rearrange it.
This is not as hard as it looks. You have factorised the left hand side and taken out a common factor of X.

Have you tried dividing both sides by (A + 2B), see what happens

3. I don't really understand what you mean. I thought rearranging was doing the reverse of what is input in a function machine. So
3X + 3 = 6 would be X --> [*3] --> [+3] = 6 reversed to be 6 -> [-3] -> [/3] = X = 1. I'm confused with brackets. Would the answer be
X = 10 ?
(A + 2B)

4. Originally Posted by Aihem
I don't really understand what you mean. I thought rearranging was doing the reverse of what is input in a function machine. So
3X + 3 = 6 would be X --> [*3] --> [+3] = 6 reversed to be 6 -> [-3] -> [/3] = X = 1. I'm confused with brackets. Would the answer be
X = 10 ?
(A + 2B)
Yes that is pretty much it.

If it is easier, try to think of "(A + 2B)" as just a number, lets say 2. If our expression was 2X on the left hand side, then you would have no problem dividing by 2 to get an expression for X.

The same rule applies for "(A + 2B)", as X is multiplied by the whole of this bracket, then we can just divide both sides by (A + 2B), you are then left with:

$\displaystyle X = \frac{10}{A + 2B}$

Hope this clears it up a bit

5. So
X(3A + B) = Z would be X = Z/ (3A + B)

I'm stuck on this one now $\displaystyle 20 = 5$
X * X
Ps. How do I get the Squared symbol?

6. Originally Posted by Aihem
So
X(3A + B) = Z would be X = Z/ (3A + B)
Yes. In "AX= Z", because X is multiplied by A, you do the opposite: divide both sides by A to get X= Z/A. It doesn't matter how complicated "A" is: in X(3A+ B)= Z X is multiplied by 3A+B so you multiply both sides by it.

I'm stuck on this one now $\displaystyle 20 = 5$
X * X
Ps. How do I get the Squared symbol?
Was this supposed to be $\displaystyle 20= \frac{5}{x^2}$?

If so, first multiply both sides by $\displaystyle x^2$, to get $\displaystyle 20x^2= 5$, then divide both sides by 20 to get $\displaystyle x^2= \frac{5}{20}k$. Finally, since x is squared on the left, "undo" that by taking the square root of both sides. That will be much easier if you reduce the fraction $\displaystyle \frac{5}{20}$!

7. What do you mean by taking the square root of both sides? How would I do that to 5/20?

8. 5/20 = 1/4. Square root of 1/4 is simply 1/2.