These functions are from my Microeconomics course. I don't know how to plot them (I haven't studied this topic in my Maths courses), so it would be really grateful if you can give me some help:
$$ \ U(x_1,x_2 )=x_1+min\{x_1,x_2\} $$
and this one: $$ \ U(x_1,x_2 )=max\{min\{x_1,4x_2\}, min\{4x_1,x_2\}\} $$
If you know some book that explains this topic, please tell me.
Thanks in advance.