Question

( căn 7 + căn 3 ) bình - ( căn 7 - căn 3 ) bình

Answer 1

=10+2căn 21-10+2căn 21

=4*căn 21

Answer 2

Lời giải:

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

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

$=4\sqrt{21}$

Answer 3

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

\(=\left[\left(\sqrt{7}+\sqrt{3}\right)-\left(\sqrt{7}+\sqrt{3}\right)\right].\left[\left(\sqrt{7}+\sqrt{3}\right)+\left(\sqrt{7}-\sqrt{3}\right)\right]\)

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

\(=2\sqrt{3}.2\sqrt{7}\)

\(=4\sqrt{21}\)

\(Hoặc\)

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

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

\(=4\sqrt{21}\)