例8求lm x→ax-a 解原式=lin(x-3a}(x-)2 x→a X-a =lim 3/2 2 x→Vx+ax+Va 令m=x-aim3n2 =0 33a2 上页例 8 lim . 33 3 x a x a x a −− → 求 解 x a x a x a x a − − − = → 3 3 3 2 ( ) ( ) 原式 lim 3 2 3 3 2 3 2 ( ) lim x ax a x a x a + + − = → 3 2 = 0 ． 3 2 0 3 lim a u u → 令u = x − a