Answer:
Minimum z =22 at A =6, B=1
See the graph below variable A is on the horizontal axis and variable B on the vertical axis
Explanation:
We can solve using the graphical method
Min z = 3A + 4B
s.t.
1A + 3B ≥ 9
1A + 1B ≥ 7
A, B ≥ 0
Draw two lines using the constraint equations
1A + 3B = 9
1A + 1B = 7
The feasible region for the inequality constraints is the region that satisfies all 4 constraints below
1A + 3B ≥ 9
1A + 1B ≥ 7
A, B ≥ 0
This is the heavily shaded region in the graph. The minimum will be at one of the corner points
There are three corner points on the graph
(0,7), (6,1) and (9,0)
Plug in these coordinate values with A being the first and B being second in the parentheses and see which set of values makes the objective function the minimum
Point (7,0) ==> z = 3(0) + 4(7) = 28
Point (6,1) ==> z = 3(6) + 4(1) = 22
Point (9,0) ==> z = 3(9)+4(0) = 27