1) (√a+2)(a-2√a+4) = (√a+2)((√a)^2-2√a+2^2)=√a^3+8
2) (x+√у)(x^2-x√y+(√y)^2)=x^3+√y^3
4) (9+3Va+a)/(3+Va)=((3-√a)(3^2+3√a+(√a)^2))/(3+√a)(3-√a) = (3^3-√a^3)/(3^2-(√a)^2)= (27-a^1/3)/(9-a)
3)(9-2V3)/(3V6-2V2)=((3√6+2√2)(9-2√3))/((3√6-2√2)(3√6+2√2))=(23√6)/46=√(3/2)