why the last exercise when x approaches to -inf, why does it happen 1/15 but not -1/15

(1 point) A function is said to have a horizontal asymptote if either the limit at infinity exists or the limit at negative infinity exists. Show that each of the following functions has a horizontal asymptote by calculating the given limit. 4X lim 13 + 2x 5x - 14 lim O +8x - 3 -5x - 14 lim -1/6 6-6x2 x2 + 3x lim -1/15 5 -15x x2+ 3x lim 1/15 X 15x