Question

giúp mình bài này với 

Answer 1

\(Q=\sqrt{\dfrac{9}{\left(1-\sqrt{7}\right)^2}}-\sqrt{\dfrac{9}{\left(1+\sqrt{7}\right)^2}}\)

\(Q=\sqrt{\dfrac{3^2}{\left(1-\sqrt{7}\right)^2}}-\sqrt{\dfrac{3^2}{\left(1+\sqrt{7}\right)^2}}\)

\(Q=\sqrt{\left(\dfrac{3}{1-\sqrt{7}}\right)^2}-\sqrt{\left(\dfrac{3}{1+\sqrt{7}}\right)^2}\)

\(Q=\dfrac{3}{\sqrt{7}-1}-\dfrac{3}{1+\sqrt{7}}\)

\(Q=\dfrac{3\sqrt{7}+3-3\sqrt{7}+3}{6}\)

\(Q=\dfrac{3+3}{6}=\dfrac{6}{6}=1\)

 

Answer 2

`= 3/(sqrt 7 - 1) - 3/(sqrt 7 + 1)`

`= (3 sqrt 7 + 3 - 3 sqrt 7 + 3)/6`

`= 1`