x1 = [2 1]; x2 = [1 3];
v1 = [0 x1(1) x1(1)+x2(1)];
w1 = [0 x1(2) x1(2)+x2(2)];
v2 = [0 x1(2) x1(2)+x1(1)];
w2 = [0 x2(2) x2(2)+x1(2)];
plot(v1,w1,'r',v2,w2,'b');

x=[1 -1 2 0 4]; y=[3 -2 5 8 11]; z=[7 1 -3 4 4.5];
lambda=2.5; mu=-3;
mu*(lambda*(x+y))-(mu*lambda)*(y+x)

(lambda+mu)*((x+y)+z)-lambda*(x+(y+z))-mu*(x+(y+z))

x=[1/sqrt(2) -1/sqrt(2) 0];
squares_x=x(1)^2+x(2)^2+x(3)^2

y=[1/sqrt(3) 1/sqrt(3) -1/sqrt(3)];
squares_y= y(1)^2+y(2)^2+y(3)^2

z=x+y;
squares_z= z(1)^2+z(2)^2+z(3)^2

v=[-1 2]; u=[2 6];  w=[2 1];
v-0.5*u+w

v_1=[1 2 1]; v_2=[2 4 0]; v_3=[3 6 -1];
v_1-2*v_2+v_3

[4 -2 1;-3 2 -1; 1 -1 1]*[-1;2.5;7]

f_1=[1 2 1];f_2=[1 3 2]; f_3=[0 1 2];
v=-2*f_1+f_2+3.5*f_3
