Giải giúp mình câu 4 vs ạ

Ta có:

`(5+2\sqrt{6})(5-2\sqrt{6})=1`

`->5-2\sqrt{6}=1/(5+2\sqrt{6})`

`->5-2\sqrt{6}=(5+2\sqrt{6})^(-1)`

`(5+2\sqrt{6})^(3x+1)=(5-2\sqrt{6})^(5x+8)`

`<=> (5+2\sqrt{6})^(3x+1)=1/((5+2\sqrt{6})^(5x+8))`

`<=>(5+2\sqrt{6})^(3x+1)=(5+2\sqrt{6})^(-5x-8)`

`<=>3x+1=-5x-8`

`<=>8x=-9`

`<=>x=-9/8`

`->B`