If you know that x is positive, it can only be one of two types of numbers: an integer or a fraction. When a positive integer is squared, the resulting integer will always be less than if a positive integer is taken to the 4th power (think of 22 and 24). If you think of a fraction, you know that a positive fraction squared is smaller:
(1 / 2)2 = 1 / 4
(1 / 2)4 = 1 / 16
1 / 4 > 1 / 16
So your answer must be a fraction less than 1.