Answer:
y = -3
Explanation:
The y-axis is a vertical line, so the perpendicular line is a horizontal line. It is generally written in the form ...
y = constant
For the line to go through the point (-5, -3), the constant must match the y-coordinate of the point: -3
y = -3 . . . . your equation
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Such a line has a slope of 0, so could be written in "slope-intercept form" as ...
y = 0x -3
We generally omit terms that evaluate to zero.