9514 1404 393
Answer:
a.
Step-by-step explanation:
For an even-index radical, ...
[tex]\sqrt[n]{x^n}=|x|\qquad\text{n even}[/tex]
This lets us simplify the given expression as follows:
[tex]\sqrt[4]{81x^6y^4}-|y|\sqrt[4]{x^6}-\sqrt[4]{16x^2}=\sqrt[4]{(3xy)^4x^2}-|y|\sqrt[4]{x^4x^2}-\sqrt[4]{2^4x^2}\\\\=3|xy|\sqrt[4]{x^2}-|xy|\sqrt[4]{x^2}-2\sqrt[4]{x^2}=\boxed{2|xy|\sqrt[4]{x^2}-2\sqrt[4]{x^2}}[/tex]
