Any straight line in the XY plane can be represented algebraically by an equation of the form          a 1 x 1  + a 2 x 2  + - - - - - - + a n x n  = b    ----------------------- (1)    Where a 1, a 2  - - - - - - a n and b are real constants. An equation of this form is called Linear Equation in the variables x 1 , x 2  - - - - - - x n .   The variables in a linear equation are sometimes called Unknown.
There are two types of linear equation such as Homogeneous Linear Equation and Non-homogeneous Linear Equation. If b = 0 then (1) is called Homogeneous Linear Equation and if b is not equal 0 the (1) is called Non-homogeneous Linear Equation.