Verified answer

9y^4 – 121x^2

(3y^2)^2 - (11x)^2

(3y^2 + 11x)(3y^2 - 11x)

It's the difference of two perfect squares.

I assume that you can take it from there.

3(3y^4 - 37x^2)

That's the most you can factor it, hope I helped!