# Thread: Need Help: (X / 4) ^ 2 * 100 = Y, X = ?

1. ## Need Help: (X / 4) ^ 2 * 100 = Y, X = ?

Hi,

I have following formula:

(X / 4) ^ 2 * 100 = Y

I would like to find out the value of X, given I have the value of Y:

X = ?

I do not know to to move the power of 2 to the other side...

Thanks

2. ## Re: Need Help: (X / 4) ^ 2 * 100 = Y, X = ?

Originally Posted by michaelkamms
Hi,

I have following formula:

(X / 4) ^ 2 * 100 = Y

I would like to find out the value of X, given I have the value of Y:

X = ?

I do not know to to move the power of 2 to the other side...

Thanks
To undo a square you have to take a square root.

3. ## Re: Need Help: (X / 4) ^ 2 * 100 = Y, X = ?

OK, got it, I think should be something like:

(Y / 100)^(1/2) * 4

4. ## Re: Need Help: (X / 4) ^ 2 * 100 = Y, X = ?

Originally Posted by michaelkamms
OK, got it, I think should be something like:

(Y / 100)^(1/2) * 4

It's actually \displaystyle \begin{align*} \pm 4\sqrt{\frac{y}{100}} \end{align*}.

5. ## Re: Need Help: (X / 4) ^ 2 * 100 = Y, X = ?

Originally Posted by michaelkamms
Hi,

I have following formula:

(X / 4) ^ 2 * 100 = Y

I would like to find out the value of X, given I have the value of Y:

X = ?

I do not know to to move the power of 2 to the other side...

Thanks
I think it will be done like this:
(X / 4) ^ 2 = Y/100
X / 4= √(Y/100)
X = 4*√(Y/100)

algebra solver

6. ## Re: Need Help: (X / 4) ^ 2 * 100 = Y, X = ?

Originally Posted by cobooboc
I think X=4/√(Y/100) ...
I don't think so , read it properly. it's a minor mistake.

7. ## Re: Need Help: (X / 4) ^ 2 * 100 = Y, X = ?

Originally Posted by michaelkamms
(X / 4) ^ 2 * 100 = Y
I would like to find out the value of X, given I have the value of Y:
X = ?
C'mon guys...keep it simple

(X / 4) ^ 2 = X^2 / 16
SO:
100X^2 / 16 = Y
X^2 = 16Y / 100
X^2 = 4Y / 25
X = +-2SQRT(Y) / 5

8. ## Re: Need Help: (X / 4) ^ 2 * 100 = Y, X = ?

Indeed. Don't forget that if $x^2=a$, then $x=\pm\sqrt{a}$, not simply $\sqrt{a}$.

9. ## Re: Need Help: (X / 4) ^ 2 * 100 = Y, X = ?

(x+y)^4 - 100(x+y)^2

(x+y)² ((x+y)² -100)

10. ## Re: Need Help: (X / 4) ^ 2 * 100 = Y, X = ?

Originally Posted by kalwin
(x+y)^4 - 100(x+y)^2

(x+y)² ((x+y)² -100)
Assuming you are trying to factorise this, you are on the right track. Now make use of the Difference Of Two Squares rule: \displaystyle \begin{align*} a^2 - b^2 = (a - b)(a + b) \end{align*}.