\begin{deff}

Given the two polynomials $f, g \in k [x_1, x_2 , \dots , x_n].$ Let $J = lcm(LM(f), LM(g))$. We define the S-polynomial of $f$ and $g$ as the linear combination

\begin{equation}

\[ S-poly(f, g) = dfrac{J}{LT(f)}$ \cdot f - \dfrac{J} {LT( g)} \cdot g \]

\end{equation}

\end{deff}

i want the section of my definition that i have bolded to show up as an equation in the center

i can't seem to figure out how to make the fractions display properly....

HELP!!!!!!!