Respuesta :

bcalle
x = -5 is a vertical line and therefore has an undefined slope.
mreijepatmat
x= -5 is a line parallel to y-axis and has no y-intercept, then the slope in undefined.
Depending on your grade, you can say the slope = tan(Ф) and in this case angle Ф = 90° and tan(90°) = undefined (or in some book →∞)