((√(a^3 )-1)/(a+2))^(-1)+1/(a+√a+1)=1/(√a-1)
((√a³)-1)/(a+2))⁻¹+1/(a+√a+1)=(a+2)/((√a³)-1)+1/(a+√a+1)=
=(a+2)/((√a-1)(a+√a+1)+1/(a+√a+1))=(a+2+√a-1)/((√a-1)(a+√a+1))=
=(a+√a+1)/((√a-1)(a+√a+1))≡1/(√a-1).