Hello, I’m taking a linear programming class and I have a previous exam with all the answers but

Hello, I'm taking a linear programming class and I have a previous exam with all the answers but I'd like to know the reason why these are the answers if anyone could explain step by step please

 

Answers are in boldface

 

 

 

1. 2x –  1   is

 

(A) a linear equation for x, y, (B) an affine function of x,y,z,  (C) a linear form in x,

 

(D) a linear constraint for x,y, (E) none of the above.

 

 

 

2.   xy  is

 

(A) a linear constraint for x, y,  (B) a linear equation for x in standard form,

 

(C) an affine function of x, y,  (D) an equation which cannot be solved, (E) none of the above.

 

 

 

3. The linear program  2x+3y -> max subject to x+y=1

 

(A) is unbounded,  (B) is infeasible,  (C)  has many optimal solutions,

 

(D) has optimal value 3,   (E) none of the above.

 

 

 

4. The function  (x+z)/y  of x,y,z is

 

(A)   an affine function of x,y,z, (B)   a linear constraint for  x,y,z,

 

(C) an  equation,  (D) not defined for some  x,y,z, (E) none of the above.

 

 

 

5. The mathematical program x/y ->min subject to |x| ≤ 1, y > 0 for two unknowns x, y

 

(A) is a linear program, (B) is infeasible, (C) has an optimal solution,

 

(D) is unbounded, (E) is not a mathematical program.

 

 

 

6. The mathematical program  x -> max,  x

 

(A) is a linear program, (B) is infeasible, (C) has an optimal solution,

 

(D) is unbounded, (E) none of the above.

 

 

 

7.The answer to the mathematical program 3x+4y -> max , x2+ y2  ≤  25 is

 

(A) max= 25  at x = 3,  y = 4,  (B) max = 30  at x = 4, y, = 3 (C) max = 50 at x = 5, y =5,

 

(D) min =-25 at x = -3, y =–4, ( E) none of the above.

 

 

 

8. The minimal total cost for the job assignment problem

 

3              2              1              4

 

3              0              2              1

 

2              5              3              6

 

3              0              1              1

 

is    (A) 4,  (B) 6,  (C) 7, (D) 8, (E) none of the above.

 

 

 

9. For each  number  t, the equation     tx= cos(t)  for unknown x

 

(A) is not linear, (B) has a solution, (C) is a linear equation, (D) has many solutions,  (E) none of the above.

 

 

 

10. 0 ≤ 0 provided that x > 1.   A) True B) False

 

 

 

11.If x > 0 and  y > 0 then xy > 0.   A) True B) False

 

 

 

12. x > 0 only if x  ≥ 2.   A) True B) False

 

 

 

13. The linear program given by the  standard tableau

 

x1            x2            x3            x4            1               

 

1              -2             0              3              0              =x5

 

-4             0              2              0              1              =x6

 

0              1              0          2         -3      -> min

 

(A) is infeasible, (B) is unbounded,  (C) has an optimal solution,

 

(D) has only 2 linear constraints, (E)  none of the above.

 

 

 

 

 

 

 

14.  The linear program given by the standard tableau

 

x1            x2            x3            x4            1               

 

1              2              0              3              0              =x5

 

4              0              -2             0              1              =x6

 

0        -1   0              2              -3             -> min

 

(A) is infeasible, (B) is unbounded., (C) has an optimal solution,

 

(D) requires at least one pivot step to solve by simplex method.

 

 

 

15. The linear program given by the standard tableau

 

x1            x2            x3            x4            1               

 

1              2              0              3              0              =x5

 

0              0              0              0         -1 =x6

 

0              -1             0              2         -3 -> min

 

(A) is infeasible, ( B) is unbounded, (C) has an optimal solution,

 

(D) has -3 as the optimal value, (E) has only one feasible solution.

 

 

 

16. The standard tableau

 

x1            x2            x3            -1              

 

0              0              0              0              -> min

 

(A) is optimal, (B) has a bad column, (C) has a bad row, (D) is not standard, (E) none of the above.

 

 

 

17. The standard tableau

 

1               

 

-1             = x1

 

0              =x2

 

-1             -> min

 

(A) is optimal. (B) has a bad column, (C) has a bad row, (D) is not standard, (E) is too small.

 

 

 

18. Pivoting the tableau

 

x              y               

 

2*            3              = -z

 

produces the tableau

 

A) -z    y               B)  x          y 

 

   1/2        -3/2          = x               2           -3/2        = z

 

C) x         y                          D) z             y                          E) x             y             

 

  1/2         3              = z          1/2            3/2           =x          1/2             -3/2          = z

 

 

 

19. The linear program x+y -> max, x≤  -1, y ≤ – 2

 

A) is infeasible. B) is unbounded. C) has an optimal solution.

 

D) has infinitely many optimal solutions. E) has -3 as the optimal solution.

 

 

 

20.The equation  x4+ y4  = 0 for x, y

 

A) has no solutions,  B) has exactly one solution, C) has infinitely many solutions.

 

 

 

21.The system x+ 2y = 3, 4x + 7y = 0 for x,y

 

A) has no solutions. B) has exactly one solution. C) has infinitely many solutions.

 

 

 

22. The set of constraints x + y > 2, 2x + 3y > 4 implies that

 

A) 4x + 5y ≥  10,  B) x ≥ 0,   C) y ≥ 1,   D) x ≤ 0,   E) none of the above.

 

 

 

23. Unless said otherwise, a number in this course means a real number.  A) True B) False

 

 

 

24. A standard tableau  with a bad row cannot  be feasible   A) True   B)False

 

 

 

25. Any linear program given by a standard tableau with a bad column is unbounded.  

 

A) True  B) False

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