First lets define what is the equation of a line:
equation of a line is
y=mx +b
So, equation in slope intercept form would be y=mx +b
To calculate the slope m we would have to use the points (2, -1) and (-3,-1) and calculate the following formula:
slope= y2-y1/x2-x1
slope=-1+1/-3-2
slope=0
Therefore, equation in slope intercept form would be for points x -1 and y -1 would be:
-1=0*-1 + b
-1=b
Hence, y= -1