(a+2/a*a-4)+(1/a+2)=(a+2)/(a-2)(a+2)+1/(a+2)=1/(a-2)+1/(a+2)=2a/(a-2)(a+2)=6/(3-2)(3+2)=6/5
=a+2/(a+2)(a-2)+1/a+2=1/a-2+1/a+2通分=2a/a*a-4a=3代入=2*3/3*3-4=6/5
括号没有用好，表达不严密。搞不懂。
