If you try to use #2# directly you get the indeterminate form #0/0#; we can try using De L'Hospital Rule deriving top and bottom and then apply the limit: #lim_(x->2)((2-sqrt(x+2))/(4-x^2))=lim_(x->2)((-1/(2sqrt(x+2)))/(-2x))=#
as #x->2# we get: #lim_(x->2)((-1/(2sqrt(x+2)))/(-2x))=1/16#