How to factorize this polynomial

[rancom]

Hi all, I am learning math and learning how to use the HP Prime as well.

How do I factorize 4x^2+36xy+81y^2 and get (2x+9y)^2 as a result?

Things I've tried in CAS view:
- factor(4x^2+36xy+81y^2) -> 36xy+4x^2+81y^2
- factors(4x^2+36xy+81y^2) -> [4*x^2+81*y^2+36*xy,1]
- simplify(4x^2+36xy+81y^2) -> 4x^2+36xy+81y^2
- collect(4x^2+36xy+81y^2) -> 4x^2+81y^2+36xy
- cfactor(4x^2+36xy+81y^2) -> 4x^2+81y^2+36xy