Question

[khanh hoa]

1, rút gọn
g, \(\sqrt{5a}\) - \(\sqrt{16a}\) + \(\sqrt{49a}\)        (a>=0)
m, \(\dfrac{20}{3+\sqrt{5}+\sqrt{2+2\sqrt{5}}}\)

Answer 1

[Nguyễn Lê Phước Thịnh]

g: \(=\sqrt{5a}-4\sqrt{a}+7\sqrt{a}\)

\(=\sqrt{5a}+3\sqrt{a}\)

b: \(=\dfrac{40}{6+2\sqrt{5}+2\cdot\sqrt{2+2\sqrt{5}}}\)

\(=\dfrac{40}{\left(\sqrt{5}+1\right)^2+\sqrt{2}\cdot\sqrt{4+4\sqrt{5}}}\)

\(=\dfrac{40}{\left(\sqrt{5}+1\right)^2+2\sqrt{2}\cdot\sqrt{\sqrt{5}+1}}\)

\(=\dfrac{40}{\left(\sqrt{\sqrt{5}+1}\right)\left[\left(\sqrt{\sqrt{5}+1}\right)^3+2\sqrt{2}\right]}\)