Question 815370
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi,
m1 = 4    Consider y = 4x  Green line (m1 = 4 )
m2 = 0.25  consider y = {{{highlight(1/4)x}}}  Blue line (m2 = (1/4)
           consider  y = {{{highlight(-1/4)x}}} Purple line {{{m[3] = (-1/4)}}}
Note: Purple perpendicular to Green (m=4)
If lines are perpendicular, their product = to {{{-1}}}
Note:  {{{4*(-1/4) = -1}}}
{{{drawing(300,300,   -6, 6, -6, 6,   grid(1),
graph( 300, 300, -6, 6, -6, 6,0,4x,x/4,-x/4))}}}