Consider the equation 2x + 4 = 0
2x = -4
Since this equation is independent of y, for all values of y, x = -2
Hence x = -2 is a line parallel to the y-axis at x = -2.
y - 5 = 0
y = 5Since this equation is independent of x, for all values of x, y = 5.
Hence the graph of y = 5 is a line parallel to the x-axis at y = 5.
Note:
The graph of x = a is a line parallel to y-axis at x=a. The graph of y=b is a line parallel to x-axis at y = b.
