To graph the lines of equation ax + by + c = 0 (b0), we isolate the variable **y** and assign values to **x**, obtaining ordered pairs that are points of the line. Thus, it is more convenient to use the equation in reduced form as it presents the isolated y.

## Coordinates of the point of intersection of lines

The intersection of the lines **r** and **s**, when it exists, is the point **P**(x, y), common to them, which is the solution of the system formed by the equations of the two lines. Let's determine the intersection point, for example, of the lines **r**: 2x + y - 4 = 0 and **s**: x -y + 1 = 0. Setting up the system and solving it, we have:

Overriding this value at x -y = -1, we have:

1 - y = -1

y = 2

Soon, **P**(1, 2) is the intersection point of the lines** r** and **s**.

Graphically, we have:

Next: Relative Positions Between Lines