Question

Answer 1

Bài 3: 

a: \(\sqrt{2}\cdot\left(\sqrt{8}+\sqrt{32}-\sqrt{98}\right)\)

\(=\sqrt{2}\left(2\sqrt{2}+4\sqrt{2}-7\sqrt{2}\right)\)

=-2

b: \(\dfrac{2}{\sqrt{5}+2}+\dfrac{2}{2-\sqrt{5}}\)

\(=2\sqrt{5}-4-2\left(\sqrt{5}+2\right)\)

\(=-8\)

c: \(\left(3+\sqrt{2}\right)\cdot\sqrt{11-6\sqrt{2}}\)

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

=7

Answer 2

Bài 4: 

a: Ta có: \(P=\left(\dfrac{1}{a+\sqrt{a}}+\dfrac{1}{\sqrt{a}+1}\right):\dfrac{\sqrt{a}-1}{a+2\sqrt{a}+1}\)

\(=\dfrac{\sqrt{a}+1}{\sqrt{a}\left(\sqrt{a}+1\right)}\cdot\dfrac{\left(\sqrt{a}+1\right)^2}{\sqrt{a}-1}\)

\(=\dfrac{\left(\sqrt{a}+1\right)^2}{\sqrt{a}\left(\sqrt{a}-1\right)}\)