Maths linear programming

圖片參考：http://i453.photobucket.com/albums/qq252/tomchan1216/ScreenHunter_04Mar191558.jpg?t=1300522006

Purple line: 3x+2y-6 = 0
Red line: y = 3
White line: x = 4
The yellow shaded region is the required constraint.
Sub. the value of the three corners of the constraint,
For (0,3): P = 3(3) = 9
For (4,3): P = -4 + 3(3) = 5
For (4,-3): P = -4 + 3(-3) = -13
So max and min of P are 9 and -13 respectively.

Or by transforming the line to the furthest point, i.e. (0,3) and (4,-3)
max of P = 3(3) = 9
and min of P = -4 + 3(-3) = -13

2011-03-19 16:08:34 補充：
The line to be transformed: -x+3y = 3
Sub P = 3 and sketch the light blue-colored line in the graph