There are already related questions to this one, but I could not transfer these solutions to my problem.
I have the system
$\sqrt{t_1^2+u_1^2}+\sqrt{t_2^2+u_2^2}\leq 1$,
$x=2t_1-u_1+2t_2+u_2$,
$y=2u_1+t_1+2u_2-t_2$,
where all variables are real valued. In Mathematica notation this is:
equ = Sqrt[t1^2 + u1^2] + Sqrt[t2^2 + u2^2] <= 1 &&
x == 2 t1 - u1 + 2 t2 + u2 &&
y == 2 u1 + t1 + 2 u2 - t2 &&
Element[{t1, u1, t2, u2}, Reals];
I would like to plot all points $(x,y)\in\mathbb{R}^2$ where there exist $t_1,u_1,t_2,u_2\in\mathbb{R}$ such that the system has a solution.
Any ideas?