Question

Rút gọn:giải bằng 3 cách

A= Căn (3 + căn5) - Căn(3 - căn5)

Làm ơn giúp mình với!!!!

Answer 1

\(A=\sqrt{3-\sqrt{5}}-\sqrt{3+\sqrt{5}}\)

C_1:A²=\(3-\sqrt{5}+3+\sqrt{5}+2\sqrt{3-\sqrt{5}}.\sqrt{3+\sqrt{5}}\)

A²=\(6+2\sqrt{\left(3-\sqrt{5}\right)\left(3+\sqrt{5}\right)}\)

A^{2=\(6+2\sqrt{9-5}\)}

A²=6+4=10

A=\(\sqrt{10}\)

Answer 2

\(A=\sqrt{\left(3+\sqrt{5}\right)}+\sqrt{\left(3-\sqrt{5}\right)}\)

\(A=\sqrt{3+\sqrt{5}}+\sqrt{3-\sqrt{5}}\)

\(A^2=3+\sqrt{5}+3-\sqrt{5}+2\sqrt{\left(3+\sqrt{5}\right).\left(3-\sqrt{5}\right)}\)

\(A^2=6+2\sqrt{9-5}\)

\(A^2=6+2\sqrt{4}\)

\(A^2=8\)

\(\Rightarrow A=\sqrt{8}\)

Answer 3

Sơn Trần Hợp 

bước 2 bạn lm sai nhé 

A² = 3-√5+3+√5-2(√3−√5).√3+√5

A² = 6 - 2√(9-5)

A² = 6-2.2

 A  = √2