Cho P=(5-2 căn bậc hai 6)^2018 (5+2

* Hướng dẫn giải

Đáp án D

Ta có $P={\left(5-2\sqrt{6}\right)}^{2018}{\left(5+2\sqrt{6}\right)}^{2019}={\left(5-2\sqrt{6}\right)}^{2018}{\left(5+2\sqrt{6}\right)}^{2018}\left(5+2\sqrt{6}\right)$

$=\left[{\left(5-2\sqrt{6}\right)}^{2018}{\left(5+2\sqrt{6}\right)}^{2018}\right]\left(5+2\sqrt{6}\right)$

$={\left[\left(5-2\sqrt{6}\right)\left(5+2\sqrt{6}\right)\right]}^{2018}\left(5+2\sqrt{6}\right)={\left(1\right)}^{2018}\left(5+2\sqrt{6}\right)=5+2\sqrt{6}$

Vậy $P\in \left(8;10\right)$.