原式=[1/2(a+2b)(a-2b)-3(a+2b)]/[2/3(a+2b)]
=(a+2b)[1/2(a-2b)-3]/[2/3(a+2b)]
=(a/2-b-3)/(2/3)
=(1006+339-3)/(2/3)
=2013确定是对的吗？？？嗯