Question

Tính :

A =(\(\sqrt{8}\) - \(3\sqrt{2}\) + \(2\sqrt{5}\))(\(\sqrt{2}\) + \(10\sqrt{0,2}\))

Answer 1

A=(\(\sqrt{8}-3\sqrt{2}+2\sqrt{5}\))\(\left(\sqrt{2}+10\sqrt{0,2}\right)\)

= (\(2\sqrt{2}-3\sqrt{2}+\sqrt{2}\).\(\sqrt{10}\))(\(\sqrt{2}+\)\(\dfrac{10}{\sqrt{5}}\))

=\(\sqrt{2}\left(\sqrt{10}-1\right)\).(\(\sqrt{2}+2\sqrt{5}\))=\(\sqrt{2}\left(\sqrt{10}-1\right).\sqrt{2}\left(\sqrt{10}+1\right)\)

=2(10-1)=18

Answer 2

\(=\left(2\sqrt{2}-3\sqrt{2}+2\sqrt{5}\right)\left(\sqrt{2}+10\sqrt{\dfrac{1}{5}}\right)\)

\(=-2-10\sqrt{\dfrac{2}{5}}+2\sqrt{10}+20\sqrt{\dfrac{5}{5}}\)

\(=-2-\dfrac{10\sqrt{2}}{\sqrt{5}}+2\sqrt{10}+20\)

\(=-2-2\sqrt{10}+2\sqrt{10}+20\)

\(=18\)