48th Polish Mathematical Olympiad Problems 1997

48th Polish Mathematical Olympiad Problems 1997A1.  The positive integers x1, x2, ... , x7 satisfy x6 = 144, xn+3 = xn+2(xn+1+xn) for n = 1, 2, 3, 4. Find x7. A2.  Find all real solutions to 3(x2 + y2 + z2) = 1, x2y2 + y2z2 + z2x2 = xyz(x + y + z)3.