Question 1045523
{{{drawing(300,300,   -6, 6, -6, 6, grid(1), 

blue(line(-1,-2,5,4)) ,
blue(line(-1,-2,-3,0)) ,
blue(line(-3,0,5,4)) ,
graph( 300, 300, -6, 6, -6,0  ))}}}
(-1 -2), (5 4),  m = -6/-6 = 1
(-1 -2), (-3,0),  m = 2/-2=  -1   lines are perpendicular at P(-1,-2)