$$\Bigsum_{i=\1}^{n-\1}\frac1{\Del~x}\Bigint_{x_i}^{x_{i+\1}}\{\frac1{\Del~x}\big[(x_{i+1}-x)y_i^{5$\star}\big]-f(x)\}^\2dx$$
Thanks to some great collaborative Moodling driven by Zbigniew Fiedorowicz, Moodle 1.2 will natively and efficiently support embedded mathematics notation! 
It's easy to edit (using standard TeX notation) anywhere in Moodle (forums, journals, quizzes, assignments etc), and works on any browser! 