(4)设limf(n)=Aim(x)=b2,且 l→>l0 x≠x→0(x)≠ limfl()=Ax x ≠ ⇒0 0 ϕ ( x) ≠ u ⑷设 ( ) ( ) 且 0 0 lim ,lim , u u x f u A ϕ x u → = = ，则 ( ) 0 lim . x x f ϕ x A → ⎡ ⎤ = ⎣ ⎦