Question

Tính:

\(\left(\sqrt{8}-2\sqrt{32}+3\sqrt{50}\right)+\left(\dfrac{1}{3+2\sqrt{2}}-\dfrac{1}{3-2\sqrt{2}}\right)\)

Answer 1

= 5 căn 2

Answer 2

= \(\left(2\sqrt{2}-8\sqrt{2}+15\sqrt{2}\right)\left[3-2\sqrt{2}-\left(3+2\sqrt{2}\right)\right]\)

= \(9\sqrt{2}\left(3-2\sqrt{2}-3-2\sqrt{2}\right)\)

= \(9\sqrt{2}\left(-4\sqrt{2}\right)\)

= \(-9.2.4\)

= \(-72\)

Answer 3

\(\left(\sqrt{8}-2\sqrt{32}+3\sqrt{50}\right)+\left(\dfrac{1}{3+2\sqrt{2}}-\dfrac{1}{3-2\sqrt{2}}\right)\)

\(=\left(2\sqrt{2}-8\sqrt{2}+15\sqrt{2}\right)+\left[3-2\sqrt{2}-\left(3+2\sqrt{2}\right)\right]\)

\(=\left(9\sqrt{2}\right)+\left(3-2\sqrt{2}-3-2\sqrt{2}\right)\)

\(=9\sqrt{2}+\left(-4\sqrt{2}\right)\)

\(=9\sqrt{2}-4\sqrt{2}\)

\(=5\sqrt{2}\)