Unit 5: Linear Equations and Inequalities

Class 9 Mathematics | Punjab Curriculum and Textbook Board Syllabus 2025

1. Define linear equation.

An equation of the form \( ax + b = 0 \), where \( a \) and \( b \) are constants, \( a \neq 0 \), and \( x \) is a variable, is called a linear equation in one variable.

General Form: \( ax + b = 0 \), where \( a \neq 0 \)

Note: The highest power of the variable in a linear equation is always 1.

2. Define inequality.

A mathematical statement that expresses a relationship between two expressions that are not equal.

Symbols:

  • \( > \) Greater than
  • \( < \) Less than

Symbols:

  • \( \geq \) Greater than or equal to
  • \( \leq \) Less than or equal to

3. Define linear inequality in one variable.

A linear inequality in one variable \( x \) is of the form:

\( ax + b < 0 \), where \( a, b \in \mathbb{R} \), \( a \neq 0 \)

Note: The \( < \) symbol can be replaced by \( > \), \( \leq \), or \( \geq \).

4. What are problem constraints in real-world problem solving?

In real-world problem solving, each linear inequality associated with a particular problem is called a problem constraint.

The collection of these linear inequalities for a given problem is referred to as problem constraints.

5. What are decision variables in a system of inequalities?

The variables used in systems of inequalities must satisfy non-negative constraints (zero or positive values). These variables are crucial for decision-making and are called decision variables.

6. What is the feasible region?

The area confined to the first quadrant that satisfies all given constraints is known as the feasible region.

7. What is a feasible solution?

Every point within the feasible region represents a valid feasible solution to the system of linear inequalities.

8. What is a corner point (vertex)?

A point of a solution region where two boundary lines intersect is called a corner point or vertex of the solution region.

9. What is an objective function?

A function which is to be maximized or minimized is called an objective function.

10. What is an optimal solution?

The feasible solution which maximizes or minimizes the objective function is called the optimal solution.