### Theory:

Straight line:

An equation of first degree and of the form $$ax + by + c = 0$$ is called as "straight line" in $$xy$$ - plane.

Here, $$x$$ and $$y$$ are variables,

$$a$$, $$b$$ and $$c$$ are real numbers, and atleast one of $$a$$, $$b$$ are non - zero.

The graphical representation of a straight line is:

Equation of coordinate axes
The $$X$$ - axis and $$Y$$ - axis together form the graph, and they are called the cartesian plane or the coordinate axes.

A point on the coordinate axes:

If a point lies on the $$x$$ - axis, then the coordinate of the point is $$(x,0)$$.

The equation of a point lying on the $$x$$ - axis is $$y = 0$$.

Consider plotting the points on the $$x$$ - axis and observe the equation we get:

Similarly, if a point lies on the $$y$$ axis, then the coordinate of the point is $$(0,y)$$.

The equation of the point on the $$y$$ axis is $$x = 0$$.

Consider plotting the points on the $$y$$ axis and observe the equation we get: