Draw the graph of linear equations v = x and y = -x on the same cartesian plane. What do you observe?

Here, first equation is y = x.

When x = 0, then y = 0

When x = 1, then y = 1

When x = 2, then y = 2

Table for y = x is

and second equation is y = - x.

When x = 0, then y = 0

When x = 1, then y = -1

When x = 2, then y = -2

Table for y = - x is

Now, the graph for both the equations are shown below

Clearly, both the lines intersect each other at origin.