I am new in Latex, I am trying to write the Equation below, but I have some errors, I couldn't find them.
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{split}
E_q_2(A,B)
&=\frac{1}{3n}\sum_{i=1}^{n}\frac{(1-e^{{-\mu}_A(x_i)})\times(1-e^{-\mu_B(x_i)})}{{(1-e^{{-\mu}_A(x_i)})}^2+{(1-e^{-\mu_B(x_i)})}^2-[(1-e^{{-\mu}_A(x_i)})\times(1-e^{-\mu_B(x_i)})]}\\
&+ \frac{(1-e^{-(1-v_A(x_i))})\times(1-e^{-(1-v_B(x_i))})}{{(1-e^{-(1-v_A(x_i))})}^2+{(1-e^{-(1-v_B(x_i))})}^2-[(1-e^{-(1-v_A(x_i))})\times(1-e^{-(1-v_B(x_i))})]}\\
&+\frac{(1-e^{-\frac{1}{2}(1+\mu_A(x_i)-v_A(x_i))})\times(1-e^{-\frac{1}{2}(1+\mu_B(x_i)-v_B(x_i))})}{
\splitfrac{{(1-e^{-\frac{1}{2}(1+\mu_A(x_i)-v_A(x_i))})}^2+{(1-e^{-\frac{1}{2}(1+\mu_B(x_i)-v_B(x_i))})}^2 -}\\
&{[(1-e^{-\frac{1}{2}(1+\mu_A(x_i)-v_A(x_i))})\times(1-e^{-\frac{1}{2}(1+\mu_B(x_i)-v_B(x_i))})]}}
\end{split}
\end{equation}
\end{document}
Edit by @koleygr: (in order of subscripts but removed \splitfrac
too)
Corrected MWE:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{split}
E_{q_2}(A,B)
&=\frac{1}{3n}\sum_{i=1}^{n}\frac{(1-e^{{-\mu}_{A}(x_i)})\times(1-e^{-\mu_{B}(x_i)})}{{(1-e^{{-\mu}_{A}(x_i)})}^2+{(1-e^{-\mu_{B}(x_i)})}^2-[(1-e^{{-\mu}_{A}(x_i)})\times(1-e^{-\mu_{B}(x_i)})]}\\
&+ \frac{(1-e^{-(1-v_{A}(x_i))})\times(1-e^{-(1-v_{B}(x_i))})}{{(1-e^{-(1-v_{A}(x_i))})}^2+{(1-e^{-(1-v_{B}(x_i))})}^2-[(1-e^{-(1-v_{A}(x_i))})\times(1-e^{-(1-v_{B}(x_i))})]}\\
&+\frac{(1-e^{-\frac{1}{2}(1+\mu_{A}(x_i)-v_{A}(x_i))})\times(1-e^{-\frac{1}{2}(1+\mu_{B}(x_i)-v_{B}(x_i))})}{
{(1-e^{-\frac{1}{2}(1+\mu_{A}(x_i)-v_{A}(x_i))})}^2+{(1-e^{-\frac{1}{2}(1+\mu_{B}(x_i)-v_{B}(x_i))})}^2 -[(1-e^{-\frac{1}{2}(1+\mu_{A}(x_i)-v_{A}(x_i))})\times(1-e^{-\frac{1}{2}(1+\mu_{B}(x_i)-v_{B}(x_i))})]}
\end{split}
\end{equation}
\end{document}
\mu_A(x_i)
that should be\mu_{A}(x_i)
(or\mu_{A(xi)}
-added this to make you understand that TeX doesn't know how to behave on this situation). The curly brackets are really needed there for TeX to recognize what exactly of all this stuff is the subscript. Also, there are some commands came from a package you haven't add in your MWE (at least\splitfrac
). Finally, to break such a function, the best way is to declare other functions likeE(A,x_i)=\left(1-\mu_{A}(x_i)-v_{A}(x_i)\right)
and go on ...\left(\begin{array}{@{}l@{}l@{}}<First Term> & <Some Terms>\\&<Rest of the terms>\end{array}\right)
.