\documentclass[12pt]{article}

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\begin{document}
\[
C'_B\left(v\right) = C_B\left(v\right)\frac{2}{\left(n - 1\right)\left(n - 2\right)}
=
C_B\left(v\right)\frac{2}{n^2-3n+2}
\]
\end{document}