Question

Tính giá trị của A=(1-\(\sqrt{7}\)).\(\dfrac{\sqrt{7}+7}{2\sqrt{7}}\)

Answer 1

\(A=\left(1-\sqrt{7}\right)\cdot\dfrac{\sqrt{7}+7}{2\sqrt{7}}=\dfrac{\sqrt{7}-7+7}{2\sqrt{7}}=\dfrac{\sqrt{7}}{2\sqrt{7}}=\dfrac{1}{\sqrt{7}}\)

Answer 2

`A=(1-\sqrt{7}). [\sqrt{7}+7]/[2\sqrt{7}]`

`A=[(1-\sqrt{7}). \sqrt{7}(1+\sqrt{7})]/[2\sqrt{7}]`

`A=[(1-7).\sqrt{7}]/[2\sqrt{7}]`

`A=[-6]/2=-3`