Question

Rút Gọn

Answer 1

Lời giải:

a.

$=(\sqrt{2^2.7}-\sqrt{2^2.3}-\sqrt{7})\sqrt{7}+2\sqrt{21}$

$=(2\sqrt{7}-2\sqrt{3}-\sqrt{7})\sqrt{7}+2\sqrt{21}$

$=(\sqrt{7}-2\sqrt{3})\sqrt{7}+2\sqrt{21}$

$=7-2\sqrt{21}+2\sqrt{21}=7$

b.

$=11+2\sqrt{30}-\sqrt{2^2.30}=11+2\sqrt{30}-2\sqrt{30}=11$

Answer 2

a: ta có: \(\left(\sqrt{28}-\sqrt{12}-\sqrt{7}\right)\cdot\sqrt{7}+2\sqrt{21}\)

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

=7

b: Ta có: \(\left(\sqrt{6}+\sqrt{5}\right)^2-\sqrt{120}\)

\(=11+2\sqrt{30}-2\sqrt{30}\)

=11