[3a/(a-1) - a/(a+1)]*(a^2-1)/a=a[3/(a-1) - 1/(a+1)]*(a^2-1)/a=[3/(a-1) - 1/(a+1)]*(a^2-1)=[3(a+1)-(a-1)]/[(a-1)(a+1)]*(a^2-1)=[3a+3-a+1]/(a^2-1)*(a^2-1)=3a+3-a+1=3a-a+1+3=2a+4=2(√2-2)+4=2√2-4+4=2√2
