先化简后求值：1／a+1-a+3／a²-1*a²-2a+1/a²+4a+3
问题描述：
先化简后求值：1／a+1-a+3／a²-1*a²-2a+1/a²+4a+3
答
原式=[(a-1-a-3)/(a+1)(a-1)][(a-1)²/(a+1)(a+3)]
=[-4/(a+1)(a-1)][(a-1)²/(a+1)(a+3)]
=-4(a-1)/[(a+1)²(a+3)]