Question 1113645
The line is y=5  (I hope this is obvious to you.  If not, think about it for a little while. )
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{{{ drawing(300,300, -10,10,-10,10, grid(0), 
                  green( line(-10,5,10,5) ),
                 locate(-4,5.5, "+"), 
            locate(-5.5,6.5, "(-4,5)"), 
              locate(3,6.2, "y=5") 
)  }}}

Slope is rise/run = (change in y value) / (change in x value)  = 0