Line equation in slope-intercept form $\"\"$ , where $\"\"$ is slope and $\"\"$ is $\"\"$ -intercept.

$\"\"$ - axis is a horizontal line.

Slope of a horizontal line is zero.

$\"\"$ .

$\"\"$ - axis intercepts the $\"\"$ -axis at origin $\"\"$ .

$\"\"$ .

Substitute the values $\"\"$ and $\"\"$ in $\"\"$ .

$\"\"$

Equation of the $\"\"$ - axis is $\"\"$ .