Question

Bài 1: Thực hiện phép tính) 

A = (2\(\sqrt{5}\).\(\sqrt{2}\) - 3\(\sqrt{40}\)+\(\sqrt{90}\): 3): \(\sqrt{640}\)

 

Answer 1

$A=\left(2\sqrt5.\sqrt2-3\sqrt{40}+\sqrt{90}:3\right):\sqrt{640}$

$=\left(2\sqrt{5.2}-3\sqrt{2^2.10}+\sqrt{3^2.10}:3\right):\sqrt{8^2.10}$

$=\left(2\sqrt{10}-6\sqrt{10}+\sqrt{10}\right):8\sqrt{10}$

$=-3\sqrt{10}:8\sqrt{10}=\frac{-3}{8}$