
In a coordinate plane the horizontal line is called the xaxis and the vertical line is called the yaxis. The point of intersection of these axes is called the origin.QuadrantsIn the above diagram, X and Y axes divided the plane into four regions and these regions are called Quadrants and they are numbered Q_{1}, Q_{2}, Q_{3} and Q_{4}, in the anti clock wise direction the first quadrant is denoted as Q_{1}, the second quadrant is denoted as Q_{2}, the third quadrant as Q_{3} and the fourth quadrant as Q_{4}. The right hand side towards east form the Yaxis is considered as positive direction. The left hand side towards west from the Yaxis is considered as negative directions. The upward direction towards north from Xaxis is positive direction and the downward side towards the south is negative direction.
In the first quadrant Q_{1} the coordinates x and y are (+,+). That is a positive real number and a positive real number.
Plotting of Points on a Graph Paper
In the above graph the point P is at the distance of 3 units from Yaxis and 4 units from Xaxis. The ordered pair corresponding to the point P is (3,4). If we observe the points A (2,3) and B is (3,2) in the above graph, the ordered pairs of A and B denote two different points. Hence (2,3) is not equal to (3,2).
Plotting of negative coordinates:
Graph For Equation(4,0),(3,0),(2,0),(1,0),(0,0),(1,0),(2,0),(3,0),(4,0).
Observing the above graph:
1. All points lie on Xaxis.
Plot the following points on a graph sheet.
Observing the above graph:
1. All these points lie on Yaxis.
Draw a graph for y ³ x + 3.

x  4  3  2  1  0  1  2 

y = x + 3  1  0  1  2  3  4  5 
Ordered pairs  (4,1)  (3,0)  (2,1)  (1,2)  (0,3)  (1,4)  (2,5) 
To find out the region for y ³ x + 3, first we find out that the origin lies in the region represented by the graph or not.
We substitute the coordinates of the origin (0,0) in the given inequation,
y ³ x + 3, we get,
0 ³ 0 + 3
0 ³ 3, this is wrong.
The origin does not lie in the half plane represented the graph.
Graph for y ³ x + 3, is
The boundary line y = x + 3 lies in the region represented by above graph. The boundary line is drawn as a dark line. The region indicated by the graph is shaded.
Its solution set is {(x,y)/(x,y) Î
R and y ³ x + 3}