% Problem 1
 
 E = 70*10^9; % 70 GPa
 A = 100*(1/1000)^2; % 100 mm
 L = 2; % m
 P = 20*10^3; % 20 kN 
 
 % K Matrix
 
 K = [1 0 0 0; 0 1 0 -2*sqrt(3); 0 0 3 sqrt(3); 0 -2*sqrt(3) 3 sqrt(3)];
 
 % Force
 
 Q = (E*A/L)*[1;0;0;0]
 
 K_inverse = inv(K)
 
 size(Q')
 size(K_inverse)
 
 q = K_inverse*Q;