例7 a2+…+a Im enel(4+n+…+a)-nl lim n[In(ai +a2 ++ar-InnI e x→0 而 lim nx[In(ax+a2+…+an)-mn川 ln(a1¥+…+an)-Inn nim例7 x x n x x x n a a a + + + → 1 1 2 1 1 lim (1 ) [ln( ) ln ] 1 1 2 1 1 lim nx a a a n x x n x x e + + + − → = lim [ln( ) ln ] 1 1 2 1 nx a1 a a n x n x x x e + + + − → = lim [ln( ) ln ] 1 1 2 1 nx a1 a a n x n x x x + + + − → 而 x a a n n x n x x 1 ln( ) ln lim 1 1 1 + + − = → ) 0 0 (