Question 1174655
*[invoke slope 8, -11, 5, -11]

 so, you have a horizontal line which has slope zero since it does not rise vertically

{{{ drawing( 600, 600, -10, 15, -15,10,circle(8, -11,.12),circle(5, -11,.12),
locate(8, -11,p(8,-11)),locate(5, -11,p(8,-11)),
graph( 600, 600, -10, 15, -15, 10,-11,-11)) }}}