1)Solve with graphical method a) Max Z=xy S.t x=2y 0≤x≤20 0≤y≤20 x,y≥0 b) Min F=x^2 + y^2 S.t x+y≤10 x+y≤5 2x+y≤15 x,y≥0 c) "Optimum point of a linear programming problem always lies on one of the...

1)Solve with graphical method

a) Max Z=xy
S.t    x=2y
         0≤x≤20
         0≤y≤20
         x,y≥0

b) Min F=x^2 + y^2
  S.t     x+y≤10
            x+y≤5
            2x+y≤15
            x,y≥0

c) "Optimum point of a linear programming problem always lies on one of the corner points of the graph’s feasible region" Does this also apply to nonlinear programming ?
If not Explain how to get a nonlinear programming answer (max , min) from a graph.

#graphical_method_in_nonlinear_programming

I do not want the exact answer I just want a general form of problem solving ...