## Vertex connections -> Global System of equations (4)

In order to account for the balance of the primary variables according to Eq. 3-32, it is necessary to add the second equation of element 1 to the first equation of element 2, and the third equation of element 1 to the fourth equation of element 2. If concurrently the global vertex numbering is introduced for the primary variable *T* according to Eq. 3-30, the global system of equations for our two-element-graph can be clearly written in matrix form as: