# Thread: Help rearranging an equation - need to find K

1. ## Help rearranging an equation - need to find K

Ok, maths is not my strongest point... so I need your help...

Topic is hydrogeology, I need to rearrange this to isolate K.

Hx^2=h1^2 - x/L (h1^2- h2^2) + Nx/K (L-x)

Help!!

2. $Hx^2={h1}^2 - \frac{x}{L ({h1}^2- {h2}^2)} + \frac{Nx}{K(L-x)}$

$Hx^2(L-x)={h1}^2(L-x)-\frac{x(L-x)}{L ({h1}^2- {h2}^2)}+\frac{Nx}{K}$

$\frac{Hx^2(L-x)}{Nx}=\frac{{h1}^2}{Nx}-\frac{x}{L ({h1}^2- {h2}^2)Nx}+\frac{1}{K}$

$\frac{Hx^2(L-x)}{Nx}-\frac{{h1}^2}{Nx}+\frac{x}{L ({h1}^2- {h2}^2)Nx}=\frac{1}{K}$

$K=\frac{1}{\frac{Hx^2(L-x)}{Nx}-\frac{{h1}^2}{Nx}+\frac{x}{L ({h1}^2- {h2}^2)Nx}}$

3. Zarathustra - thanks for the help

appologies for the basic maths help here, but I need to fully understand this:

so you:
multiplied by (L-x) to isolate k
divided by Nx to give 1/k

thisis where I get a bit confused

subtracted Hx^2(L-x) / Nx to isolate 1/k

divide by 1 to give k = .......

I have got values for h1, h2, L x and N. I will plug them in and see what I get.

Thanks again for the help.

4. Hmmm... for the part where you confused a bit...

Imagine ( ) that $\frac{Hx^2(L-x)}{Nx}-\frac{{h1}^2}{Nx}+\frac{x}{L ({h1}^2- {h2}^2)Nx}=M$

Hence:

$M=\frac{1}{K}$

$KM=1$

$K=\frac{1}{M}$