thực hiện phép tính: a) ( √ √$\frac{1}{7}$ -√$\frac{16}{7}$ +√7) :√7 b)

$(\sqrt{\dfrac{1}{7}} – \sqrt{\dfrac{16}{7}} + \sqrt{7}):\sqrt{7}$

$=\dfrac{1}{\sqrt{7}}: \sqrt{7}- \dfrac{4}{\sqrt{7}}: \sqrt{7} + \sqrt{7}:\sqrt{7}$

$=\dfrac{1}{\sqrt{7}.\sqrt{7}} – \dfrac{4}{7} + 1$

$=\dfrac{1}{7} + \dfrac{3}{7} = \dfrac{4}{7}$