Question 175962
y=-2x+3 
y= 2x+3
{{{ graph( 300, 200, -6, 5, -10, 10, -2x +3, 2x +3) }}} (graph 300x200 pixels, x from -6 to 5, y from -10 to 10, of TWO functions -2x +3 and 2x +3). 
These 2 lines are perpendicular because the slopes are negative recipricals of the other.