2a/a2-4-1/a-2=2a/a2-4-(a+2)/a2-4=(2a-a-2)/a2-4=(a-2)/a2-4=1/a+2=1/根号3=根号3/3
2a/a²-4-1/a-2=2a/(a+2)(a-2)-(a+2)/(a-2)=(2a-a-2)/(a+2)(a-2)=(a-2)/(a+2)(a-2)=1/(a+2)=1/(√3-2+2)=1/√3=√3/3
