Machine-translated by Google. Questions are authored in English.
Top

Discussion

The graph given below shows the bounded feasible region (in shaded portion) for the problem :

Max. \(z = 2x_{1} + x_{2} - 12,\)
\(x_{1}, x_{2} \ge 0.\)

Graph in the x1 x2 plane: the shaded feasible region is the polygon with corners (0, 0), P(4, 0), Q(4, 2), R(2, 6), S(1, 7) and T(0, 7), drawn on a grid; the point (3, 4) is marked on the edge from R to Q

The objective function attains its maximum when :

  • A.\(x_{1} = 1\) and \(x_{2} = 7\)
  • B.\(x_{1} = 3\) and \(x_{2} = 4\)
  • C.\(x_{1} = 3\) and \(x_{2} = 3\)
  • D.\(x_{1} = 3\) and \(x_{2} = 5\)

Answer: B

The maximum is attained at \(x_{1} = 3\) and \(x_{2} = 4\).

The constant \(-12\) does not affect where the maximum lies, so compare \(2x_{1} + x_{2}\) at the corners: (0, 0) gives 0, P(4, 0) gives 8, Q(4, 2) gives 10, R(2, 6) gives 10, S(1, 7) gives 9 and T(0, 7) gives 7.

The edge from R to Q has slope \(-2\), the same as the objective's level lines \(2x_{1} + x_{2} = c\), so every point of that edge is optimal with value 10 (z = \(-2\)). The marked point (3, 4) lies on it: \(2 \cdot 3 + 4 = 10\).

(1, 7) gives only 9, (3, 3) is interior and gives 9, and (3, 5) lies outside the region, beyond the edge RQ, so it is not feasible.

No comment is present. Be the first to comment.
Loading…

Post your comment

Please log in or register to post a comment.