Question 278990
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The equation *[tex \LARGE y\ =\ -2] has a solution set that consist of every possible ordered pair where the *[tex \LARGE y]-coordinate is -2.  Since the value of the function is a fixed number, there is no variation in the vertical direction, either up or down -- hence it is horizontal.


John
*[tex \LARGE e^{i\pi} + 1 = 0]
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