View source for 2019 Mock AMC 10B Problems/Problem 3

After trying each option we have 
<cmath></cmath>A) <math>3^(2018/3)</math> which isn't rational as 2018 is not divisible by 3<math>
<cmath></cmath>B) </math>3^(2019/2)<math> which isn't rational as 2019 isn't divisible by 2</math>
<cmath></cmath>C) <math>3^2+\sqrt{2}^2+6\sqrt{2}</math> which equals <math>11+6\sqrt{2}</math> which is irrational<math>
<cmath></cmath>D) </math>(2pi)^2<math> equals </math>4pi^2<math> which is irrational</math>
<cmath></cmath>E) <math>(3-\sqrt{2})(3+\sqrt{2})=9-2=7</math> which is rational<math>
We have </math>\boxed{\bold{E}}<math> </math>(3-\sqrt{2})(3+\sqrt{2})$