Linear Programming (LPP) | Class 12 Maths

📌 1. Introduction

Linear Programming helps us find the best possible solution under given conditions.

👉 Example:

  • Maximizing profit
  • Minimizing cost
  • Efficient use of resources

📖 2. Basic Terminology


🔹 1. Decision Variables

The variables whose values we need to determine.

Example:x,yx, yx,y


🔹 2. Objective Function

A linear function that needs to be maximized or minimized.


Z=ax+byZ = ax + byZ=ax+by


🔹 3. Constraints

Restrictions on variables, expressed as linear equations or inequalities.

Example:ax+bycax + by \leq cax+by≤c


🔹 4. Non-Negativity Constraints

x0,y0x \geq 0, \quad y \geq 0x≥0,y≥0


📊 3. Mathematical Formulation of LPP

General form:

Maximize/Minimize:Z=ax+byZ = ax + byZ=ax+by

Subject to:a1x+b1yc1a_1x + b_1y \leq c_1a1​x+b1​y≤c1​ a2x+b2yc2a_2x + b_2y \leq c_2a2​x+b2​y≤c2​ x,y0x, y \geq 0x,y≥0


📐 4. Graphical Method

The graphical method is used to solve LPP involving two variables.


📌 Steps:

1. Convert inequalities into equations

2. Plot lines on graph

3. Identify feasible region

4. Find corner points

5. Evaluate objective function


📊 5. Feasible Region

The region satisfying all constraints is called the feasible region.


🔹 Types:

  • Bounded region
  • Unbounded region

📌 6. Optimal Solution

The best value (maximum or minimum) of objective function.

👉 Occurs at corner points of feasible region.


📐 7. Corner Point Method

Steps:

  1. Find vertices of feasible region
  2. Evaluate objective function at each vertex
  3. Choose maximum/minimum value

📊 8. Special Cases


🔹 1. Unique Solution

Only one optimal solution


🔹 2. Infinite Solutions

More than one optimal solution


🔹 3. Unbounded Solution

No maximum or minimum


🔹 4. Infeasible Solution

No feasible region


📌 9. Important Concepts

🔹 Convex Set

A set where line joining any two points lies completely inside the set.


🔹 Corner Point Theorem

Optimal solution occurs at extreme points.


📊 10. Applications of LPP

  • Production planning
  • Transportation
  • Diet problems
  • Resource allocation
  • Business optimization

❗ Common Mistakes

  • Wrong graph plotting
  • Incorrect feasible region
  • Ignoring non-negativity
  • Calculation errors

🧠 Exam Tips

  • Draw graph carefully
  • Mark feasible region clearly
  • Check all corner points
  • Practice NCERT problems

📚 Practice Questions

  1. Solve LPP graphically
  2. Find feasible region
  3. Determine optimal solution
  4. Identify special cases

🎯 Conclusion

Linear Programming is a practical and scoring chapter. It helps in solving optimization problems efficiently. Mastering graphical methods and understanding feasible regions will help you perform well in exams.

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