First, we need to determine their slopes
Let m1 be the slope for L1 and m2 be the slope for L2.
If m1 = m2 then the lines are parallel and if m1 = - 1 /m2 , then the lines are perpendicular.
We can find the slopes using the formula below:
For L1
(1, 7) and (3, 13)
x₁=1 y₁=7 x₂=3 y₂=13
substitute the values into the formula and evaluate
For L2
(-2, 4) and (1, 3)
x₁=-2 y₁=4 x₂=1 y₂=3
substitute the values into the formula and evaluate
Since m1 = 1 /m2, then the L1 and L2 are perpendicular.