Question 773649
Represent the contact points of the ladder on a cartesian coordinate system.  Use positive x and y axes.  Let y be the vertical position on the ladder and x represent the horizontal position on the ladder.  Your given information translates into (4,0) and (0,8).  The ladder is sloped at {{{m=-1/2}}} and the y-intercept, where the top of the ladder contacts the wall, is b=8.  The slope-intercept form for the equation is effectively the function for position upward on the ladder.  {{{highlight(y=-(1/2)x+8)}}}