Question 816906
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi,
Find the value of "a" for which the graph of the first equation is
 perpendicular to the graph of the second equation.
Ex:
y = ax - 5 ; 2y = 3x
Using the standard slope-intercept form for an equation of a line y = mx + b  
where m is the slope and b the y-intercept.  
 2y = 3x   0r  {{{y = highlight(3/2)x}}}  m = {{{3/2}}}
Perpendicular lines have slopes that are negative reciprocals of one another:
 y = ax - 5    m = {{{(-2/3)}}}   Note:  {{{(3/2)(-2/3) = -1}}}
{{{ y = highlight(-2/3)x - 5}}}
    a = {{{(-2/3)}}}
graphs of {{{y = highlight(3/2)x}}}(Green) and {{{ y = highlight(-2/3)x - 5}}}(Blue)
{{{drawing(300,300,   -6, 6, -6, 6, grid(1), 
circle(0, -5,0.3),
graph( 300, 300, -6, 6, -6, 6,0,1.5x,(-2/3)x - 5 ))}}}