Question

giai pt:

\(\left(\sqrt{28}-\sqrt{12}-\sqrt{7}\right)\sqrt{7}+2\sqrt{2}\)

Answer 1

\(\left(\sqrt{28}-\sqrt{12}-\sqrt{7}\right)\sqrt{7}+2\sqrt{2}\)

\(=\left(2\sqrt{7}-\sqrt{12}-\sqrt{7}\right)\sqrt{7}+2\sqrt{2}\)

\(=2\sqrt{7}.\sqrt{7}-\sqrt{12}.\sqrt{7}-\sqrt{7}.\sqrt{7}+2\sqrt{2}\)

\(=14-\sqrt{84}-7+2\sqrt{2}\)

\(=7-\sqrt{84}+2\sqrt{2}\)

Chúc bạn học tốt!!!

Answer 2

cách ngắn:

\(\left(\sqrt{28}-\sqrt{12}-\sqrt{7}\right)\sqrt{7}+2\sqrt{2}\)

\(=\left(2\sqrt{7}-2\sqrt{3}-\sqrt{7}\right)\sqrt{7}+2\sqrt{2}\)

\(=\left(\sqrt{7}-2\sqrt{3}\right)\sqrt{7}+2\sqrt{2}\)

\(=7-2\sqrt{21}+2\sqrt{2}\)