A formula for a [[Convergent Series|a convergent series]] using [[Forward Difference|forward differences]] to approximate the convergence point. If $\set{x_{i}}$ is close to an [[Geometric Series|offset geometric series]], then: $\huge \lim_{ n \to \infty } x_{n} \approx x_{1} - \frac{\pa{\Delta x_{1}}^{2}}{ \Delta^{2} x_{1} } $ >[!note] >This only works / is accurate if the [[Linear Convergence|convergence is linear.]] >If the convergence is non-linear, then it is more accurate to simply evaluate the series one more step than use this method.