group equation

例句：

1. 1. The group equation is used to describe the balance of forces in a system.
   群方程用于描述系统中力平衡的情况。
2. 2.In this model, the group equation is used to calculate the average value of a variable.
   在这个模型中，群方程被用来计算变量的平均值。
3. 3. The group equation was derived from the laws of thermodynamics.
   群方程是从热力学定律推导出来的。