(a-2/a^2+2a-a-1/a^2+4a+4)÷a-4/a+2=[(a-2)/a(a+2)-(a-1)/(a+2)^2] ×(a+2)/(a-4)=[(a-2)/a-(a-1)/(a+2)] ×1/(a-4)=(a^2-4-a^2+a)/a(a+2) ×1/(a-4)=(a-4)/a(a+2) ×1/(a-4)=1/a(a+2) =1/(√2-1)(√2+1)=1/(2-1)=1
