Final answer:
The equation of a horizontal line passing through the point (-3,-6) is y = -6, as horizontal lines have a slope of 0 and the y-coordinate remains constant.
Step-by-step explanation:
The equation of a horizontal line that passes through the point (-3,-6) is y = -6. A horizontal line has a slope of 0, which means there is no rise over run, and therefore, the value of y does not change regardless of the value of x.
According to the slope-intercept form of a linear equation, y = mx + b, the value of m (the slope) is 0, and b (the y-intercept) is the y-coordinate of the point the line passes through, which is -6 in this case.