it sure would be nice if you learned to use LaTex. It's not that hard.

Is this what you mean?

$w(x)=\displaystyle \prod_{i=1}^n \left(x-x_i\right)$ prove that

$f\left(x_0, x_1,\dots, x_n\right)=\displaystyle{\sum_{i=0}^n} \dfrac{f(x_i)}{\dfrac{dw}{dx_i}}$

and calculate

$\displaystyle \lim_{x_2 \to x_1}f\left(x_0, x_1,\dots, x_n\right)$