Respuesta :
slope for (x1,y1) and (x2,y2) is (y2-y1)/(x2-x1)
for (2,-3) and (2,9) the slope is (9-(-3))/(2-2)=(9+3)/0= wait, dividing by 0 is undefined
the slope is undefined
for (2,-3) and (2,9) the slope is (9-(-3))/(2-2)=(9+3)/0= wait, dividing by 0 is undefined
the slope is undefined