Answer:
9x^8
Explanation:
A perfect square is a number that has a whole number square rooth. Therefore we need to find two numbers 'a' and 'b' that satisfy the following equation:
3x^4 = sqrt(ax^b)
(3x^4)^2 = ax^b
9x^8 = ax^b
a=9 and b=8.
Therefore, the term 9x^8 is a perfect square of the root 3x^4.