@glorfindel133 Yes.. at 2:14 , x1 becomes basic variable and s2 leaves basic variables (these actions are based on which was pivot column and row respectively)... since x1 turns to a basic variable, we should have value 1 where x1 (basic variables, vertical order) crosses itself (horizontal order) ... since the pivot number was 2 (initial table), we divide by 2 to get that value 1 (2nd table), but we have also to divide by 2 (apply the same operation on) the rest elements of the pivot row.
However, a min problem, with all constraints <=, can easily have, not bounded solution (when constraints have at least one negative term) or trivial solution {0,0,0} (all constraints have only positive terms, our case study: for {1,0,0} or {0,2,0} zz is negative, so max zz is 0 for {0,0,0}).
The sign (+,-) in objective function's terms (not only in constraints) makes also a difference. min z=60x1 - 30x2 + 20x3 ( -30 !! ) with same constraints would have another solution (not {0,0,0} from the initial Simplex table).
An alternative way to get these 2 values : sumproduct of yellow columns at right , that is (4:47) 4*60=240 (only x1 is in the basic variables) and (8:38) 2*60 + 8*20 = 120 + 160 = 280 (x1 and x3 are in the basic variables). Objective function 60x1+30x2+20x3 gets these values for solutions {4,0,0} and {2,0,8} respectively.
I want to watch" shortest path problem" with "floyd method". I didn't find. How can I find. do you have any videos about this
FreeMaNNer 8 months ago
Is it a must that a pivot number to has a value of 1 after we have already found it? I mean why do you divide row2 by 2?
glorfindel133 9 months ago
@glorfindel133 Yes.. at 2:14 , x1 becomes basic variable and s2 leaves basic variables (these actions are based on which was pivot column and row respectively)... since x1 turns to a basic variable, we should have value 1 where x1 (basic variables, vertical order) crosses itself (horizontal order) ... since the pivot number was 2 (initial table), we divide by 2 to get that value 1 (2nd table), but we have also to divide by 2 (apply the same operation on) the rest elements of the pivot row.
mathm09 9 months ago
Lost it when we got to the 2nd Simplex tableau. T_T
Chey456 10 months ago
managerial accounting
vikashmeetoo 11 months ago
this video would be much better with audio...
photojoebill1989 1 year ago 4
This video would be much better if you had audio, and didn't move so fast. Really hard to follow with the speed...
photojoebill1989 1 year ago
@evolutionoforage
However, a min problem, with all constraints <=, can easily have, not bounded solution (when constraints have at least one negative term) or trivial solution {0,0,0} (all constraints have only positive terms, our case study: for {1,0,0} or {0,2,0} zz is negative, so max zz is 0 for {0,0,0}).
mathm09 1 year ago
@evolutionoforage
The sign (+,-) in objective function's terms (not only in constraints) makes also a difference. min z=60x1 - 30x2 + 20x3 ( -30 !! ) with same constraints would have another solution (not {0,0,0} from the initial Simplex table).
mathm09 1 year ago
@evolutionoforage
Note: First row in 1st table is 60 30 20 0 0 0 0 , last row in 1st table is -60 -30 -20 0 0 0 0
and termination rule is " no <0 values in last row" (optimal solution).
In many textbooks: First row in 1st table is 60 30 20 0 0 0 0 last row in 1st table is also 60 30 20 0 0 0 0
and termination rule is inversed " no >0 values in last row" (optimal solution).
Both ways, algorithm's conclusions are the same.
mathm09 1 year ago
@evolutionoforage
Sorry, not checking this email account regularly...
Consider f(x)=x^2+3x+6 (U shape) ... min f(x) = 3.75 at x= -1.5
Consider g(x)= -f(x) = -x^2-3x-6 (inverse U shape) ... max g(x) = -3.75 at x= -1.5
Conclusion: min f(x)= -max g(x) = - max (-f(x))
So, maximize zz = -60x1 -30x2 - 20x3 . x1, x2 , x3 will be the same with min z=60x1+ 30x2 + 20x3 , but optimal solution is z = -zz
So , you start with -60 -30 -20 etc.
mathm09 1 year ago
Thank you, very helpful
yusefsobky 2 years ago
Thank you!
wikiih 2 years ago
I kind of got lost there. How did you get 240 and 280 at the end. I couldn't follow the logic. Please explain. Thanks.
bubbles20092010 2 years ago
value 240 at 4:47 ...
r5 ' = r5 - (-60) r2 ' = r5 +60 r2 ' = 0 + 60*4 = 240
value 280 at 8:38 ...
r5 '' = r5' - (-5) r1 '' = r5 ' +5 r1 '' = 240 + 5*8 = 240 + 40 = 280
An alternative way to get these 2 values : sumproduct of yellow columns at right , that is (4:47) 4*60=240 (only x1 is in the basic variables) and (8:38) 2*60 + 8*20 = 120 + 160 = 280 (x1 and x3 are in the basic variables). Objective function 60x1+30x2+20x3 gets these values for solutions {4,0,0} and {2,0,8} respectively.
mathm09 2 years ago
Really good video. Taught us perfectly :)
HamsterHam88 2 years ago