To rationalize the denominator we have to multiply it by the conjugate, as follows:
[tex](3+\sqrt{6})(3-\sqrt{6})=3^2-(\sqrt{6}\rparen^2[/tex]
The latter considering the property (a-b)(a+b)=a^2-b^2.
Finally we have:
[tex]3^2-6=9-6=3[/tex]
The the answer is D. 3
