求1/a+1-a+3/a方-1*a方-2a+1/a方+4a+3的值
问题描述：
求1/a+1-a+3/a方-1*a方-2a+1/a方+4a+3的值
答
1/(a+1)-(a+3)/(a^2-1)*(a^2-2a+1)/(a^2+4a+3) =1/(a+1)-[(a+3)(a-1)(a-1)]/[(a+1)(a-1)(a+3)(a+1)] =1/(a+1)-(a-1)/(a+1)^2 =[(a+1)-(a-1)]/(a+1)^2 =2/(a+1)^2