To determine if lines are parallel, perpendicular or neither, we need o determine each line's slope.

If slopes are equals then they are parallel.

Let us calculate L1 slope (m1)

m1= (y2-y1)/(x2-x1) = (4-4)/(0+1)= 0

slope 0 means that the line L1 is horizontal or parallel to the x-axis.

Now the slope for L2 (m2):

m2= (y2-y1)/(x2-x1)= (2-6)/(5-5)= -4/0 Undefined slope

Undefined slopes means that the line L2 is vertical or parallel with y-axis

Then the lines L1 and L2 are perpendicular.

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