Answer:
![(3x^2-y^4)(3x^2-y^4)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/tlakro08rcu5rrnzyst3eqo37in4153ast.png)
Explanation:
We'll assume the correct expression to be factored is
![9x^4-6x^2y^4+y^8](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ydvti8m4il9jmqqo4h73savb7zeukax1hx.png)
One must try to find out if the expression is a perfect square. To test it, we'll take the square root of the first and the last term. If they are exact, we'll procceed with the next step
![√(9x^4)=3x^2](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ni0jyv5a2c31bxy38343d29m0k5k3zmojj.png)
![√(y^8)=y^4](https://img.qammunity.org/2020/formulas/mathematics/middle-school/f0egjs5f3rk7ldacab46tgo1etmslu9q1n.png)
Since both are exact, we'll test if the middle term is twice the product of both square roots:
![2(3x^2)(y^4)=6x^2y^4](https://img.qammunity.org/2020/formulas/mathematics/middle-school/leev8kdwrenmhh7bdss3egolcqu9ny3g72.png)
We confirm the middle term equals the above expression. All tests confirm the original expression is
![\left ( 3x^2-y^4 \right )^2](https://img.qammunity.org/2020/formulas/mathematics/middle-school/afl388przq22lrizs6xpqdgf80v2rvnggj.png)
The required factoring is
![(3x^2-y^4)(3x^2-y^4)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/tlakro08rcu5rrnzyst3eqo37in4153ast.png)