(1)解方程组得x=(8a+11)/3y=(10-2a)/3依题意，有(8a+11)/3<(10-2a)/3(8a+11)/3>0(10-2a)/3>0解之，得-11/8(2)原式=（8a+11)+(10a+1)=18a+12=6(3a+2)
