Algebraic Expressions:

Any expression involving a constant, variable and some operations like addition, multiplication etc is called Algebraic Expression.

  • A variable is an unknown number and generally, it is represented by a letter like x, y, n etc.
  • Any number without any variable is called Constant.
  • A number followed by a variable is called Coefficient of that variable.
  • A term is any number or variable separated by


A statement which says that the two expressions are equal is called an Equation.

Linear Expression:

A linear expression is an expression whose highest power of the variable is one only.

Example:    3 x   +   5,     3 y,    etc.

The expressions like  x²   +    1,      2 z²   +   3  are not linear expressions as their highest power of the variable is greater than 1.

Linear Equations:

The equation of a straight line is the linear equation. It could be in one variable or two variables.

Linear Equation in One Variable:

If there is only one variable in the equation then it is called a linear equation in one variable.

The general form is

a  x   +   b     =     c,   where  a, b and c are real numbers and a ≠ 0.

Examples:  x   +   5     =     10     and     y   –   3     =     19

These are called linear equations in one variable because the highest degree of the variable is one and there is only one variable.