What is the completely factored form of x4y - 4x2y - 5y?

y (x2 - 5) (x2 1)

y (x2 5) (x2 - 1)

(x2y - 5) (x2 1)

(x2y 5) (x2 - 1)

If you would like to write x^4y - 4x^2y - 5y in a completely factored form, you can do this using the following steps:

x^4y - 4x^2y - 5y = y * (x^4 - 4x^2 - 5) = y * (x^2 + 1) * (x^2 - 5)

The correct result would be y * (x^2 + 1) * (x^2 - 5).