(i) If x = 7 + 3√5/7 − 3√5 , find the value of x − 1/x^2 (ii) If x = √5 − √2/√5 + √2 and y = √5 + √2/√5 − √2 , find the value of x^2 + xy + y^2 (iii) If x = √3 − √2/√3 + √2 and y = √3 + √2/√3 − √2 , find the value of x^3 + y^3.