The values of displacements in {D} necessary to ensure the equilibrium of the joints are determined using the relation (displacement vector = {D}; stiffness matrix = [K]; and load vector ={P})
1
{P} + [K] {D} = 0
2
{D} + [K] {P} = 0
3
{P} {D}+ [K] = 0
4
[K] {P} = 0