Math
posted by Joanie .
I have two problemson polygonal convex sets which I do not understand.
The first: Find the minimum value of f(x,y) = 2xy+2 for the polygonal convex set determined by this system of inequalities:
x is more than or equal to 1
x is less than or equal to 3
y is more than or equal to 0
1/2x + y is less than or equal to 5
The second problem:
This system forms a polygonal convex set: x is less than or equal to 0;
y is more than or equal to x, if x is between 0 and 6.
y is less than or equal to 10; 2x + 3y is more than or equal to 6, if x is between 12 and 6.
What is the area of the closed figure?
I do not have a clue as to how to do either of these problems.

I don't know what a 'polygonal' or a 'convex' set means. Your four inequalities define a trapezoidal region of x,y space. You can easily plot it on a graph. The lowest value of 2x  y + 2 in that space occurs where x is least (1) and y is highest (4.5). At that corner of the trapezoid,
2xy+2 = 2  9 + 2 = 5
If that is what is meant by your problem, you should be able to answer the second question by a similar procedure