Answer: It's not
Step-by-step explanation:
A perfect square is always [tex](x+y)^{2}[/tex], where [tex]x^{2} +2xy+y^{2}[/tex].
Knowing this, we can square root 144x to get 12x. Square rooting 81 gets us 9. Unfortunately, if we multiply 12 and 9 together, then double it, we get 216, which is definitely not 200.
Therefore, the polynomial is not a perfect square.