LaTeX.org

I will try to explain my problem in more detail here.

I have written Eq. in pic1 in Latex:

The code is as follows:

\begin{equation}\label{eq: CP}CP= \frac{c}{\sum_{i=1}^c
\left(\frac{\sum_{x_m\in C_i,x_m\neq x_{c_i}}u_{im}^2
R_{c_im}^2}{\sum_{x_m\in C_i,x_m\neq
x_{c_i}}u_{im}^2}\right)}\end ...

I need to put a fractional backward slash in an equation. I am unable to do that. If I put a normal slash it is very small....I want it to be a big slash (slanting). Is there any command in LAtex for that.