The first picture is the formulas for the finite element method I learnt. And the second picture is an example in the textbook. I am wondering where do $2/3$ and 8/3 come from? Is it because 4*$h/6$ and 4*$2h/3$ (the first two formulas in the first picture)? And why there are only 3 elements per line? And why are the first $c_j$ and the last one per line are the same? How to calculate that? Thanks!
