16.(本题共10分,第(1)小题4分,第(2)小题6分)解:(1)原式=5+(-2)+83分=11.4分aog-aa8a+1..1fa-22a-4a+12分(a+1a-1)a-22(a-2)a+13分(a+1a-1)a-224分a-121当a=-3时,原式=.6分-3-12