Question 314410

{{{ drawing( 300,300, -5, 5, -10, 10,
blue(line(-1,10,-1,-10)),
blue(line(3,10,3,-10)),
blue(line(0,10,0,-10)),
 graph( 300,300, -5, 5, -10, 10, x*(x-3)*(x+1) )) }}}
I think you can take it from here.