a'+b"+ct!例1.求lim(a>0, b>0, c>0)3解：原式=lim(1+g+b*+c*-3)3a"+b*+c*-313=lim(l+a'+b*+c*-3a+b+c-33Y3x-0m(d-)+(6*-1)+(c-1)a+b'+c-31α-1~xlnalim3xer-03二XX0e二Ina+Inb+Inclim-3=er->0InabcInabc3=e?=abc例1. 求 1 0 lim( ) ( 0, 0, 0) 3 x x x x x abc a b c → + +    解：原式= 1 0 3 lim(1+ ) 3 x x x x x abc → + + − 3 1 3 0 3 3 3 lim(1 ) 3 x x x x x x a b x x x a b c x c x abc + + − + + − → + + − = +0 3 1 lim 3 x x x x a b c x e → + + − = 0 ( 1) ( 1) ( 1) lim 3 x x x x a b c x e → − + − + − = 0 ln ln ln lim x 3 a b c e → + + = ln 3 abc = e 3 = abc 1 ln x a x a − 3 ln abc = e