The letter "C" in the firstequation refer to "Contribution". It means the differenCe between sales revenue and variable Costs.
第一个等式中的“C”是指边际贡献，它是指销售收入和变动成本之间的差额。
2
At first we can get the Lagrangian function from the elliptic equation, then replace differential coefficient by difference and get the discrete Lagrangian function.
给定一个椭圆方程，我们先找出这个方程的拉氏函数，用差分代替微分，得到离散的拉氏函数。
3
In this paper, an implicit-explicit upwind difference scheme for the first order linear hyperbolic equation is proposed using explicit scheme and implicit scheme alternately.