(1)原式=3-8×1+ 1 2 +4=- 1 2 ;(2)原式=[ 3 a+1 - (a+1)(a?1) a+1 ]? a+1 (a?2)2 = (2+a)(2?a) a+1 ? a+1 (a?2)2 = 2+a 2?a .当a=-3时,原式= 2?3 2?(?3) =- 1 5 .