A Simple Example
To illustrate the concepts in a very simple example, assume that we're running a furniture
factory. This model has a profit equation with 2 terms, and
has 2 constraint equations, requiring a profit computation at 3 places. By
comparison, a plywood mill has a profit equation with 3400 terms, about 4600
constraint equations, and 12,000 places to compute a profit!

Our Assembly area can put together 200 chairs and/or tables a day; our
finishing area can do 100 Tables or 400 Chairs a day. These become
our constraints, shown in blue above -- we can't have an operating point
to the upper right of these lines.
Our gross margins on chairs is $5, on tables $15. The gross margin
equation is shown in dotted red for a few sample operating points.
The optimal point is at that place where the profit is maximized, but within
the constraint boundary. The solver engine moves the profit line in small
increments until it hits constraints.
Notice that the optimum point requires making fractional chairs and tables
-- clearly not possible. But the optimum operating point is +- 1
chair/table away from this point and is easily analyzed as a second step.
In the real world, there are hundreds of dimensions to the chart, and
hundreds of constraint equations, and we can no longer visualize the optimum
operating point. That's why we use Linear Programming technology, included with Enterprise Optimizer.
If we are required to keep the ratio of tables and chairs within certain
bounds, that produces a different constraint (example).