\lim_(x->4^(+))(x)/(x-4)
\lim_(t->3^(-))(t^(2))/(9-t^(2))
\lim_(x->5^(-))(x^(2))/((x-5)(3-x))
\lim_(x->3^(-))(x^(3))/(x-3)
\lim_(x->3^(-))(x^(2)-x-6)/(x-3)