Question

[nguyen thuy trang]

Cho B= \(\frac{x-2\sqrt{x}+4}{\sqrt{x}}\)(voi x>0)

Tim min B

Answer 1

[Cô Hoàng Huyền]

Ta có: \(B=\frac{x}{\sqrt{x}}-\frac{2\sqrt{x}}{\sqrt{x}}+\frac{4}{\sqrt{x}}=\sqrt{x}-2+\frac{4}{\sqrt{x}}=\left(\sqrt[4]{x}\right)^2-2.\sqrt[4]{x}.\frac{2}{\sqrt[4]{x}}+\left(\frac{2}{\sqrt[4]{x}}\right)^2+2\)

\(=\left(\sqrt[4]{x}-\frac{2}{\sqrt[4]{x}}\right)^2+2\ge2\)

Vậy Min B = 2  khi x = 4.

Chúc em học tốt :)