you should already know :

but referring back to the diagrams:

using the boundary conditions and law of equilibrium:

• $f_{2x}^{(1)}$ = F

  • you can look at it as it $f_{2x}^{(1)}$ is the actual force being applied if it helps

• $d_{1x}^{(1)}$ = 0

  • since node 1 is fixed

• now we can solve the system and get some pretty obvious results!