Question

(căn bậc 49-12 căn bậc5)-(căn bậc 49 + 12 căn bậc 5) bằng bao nhiêu

 

Answer 1

Trả lời:

\(\sqrt{49-12\sqrt{5}}-\sqrt{49+12\sqrt{5}}\)

\(=\sqrt{45-12\sqrt{5}+4}-\sqrt{45+12\sqrt{5}+4}\)

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

\(=3\sqrt{5}-2-3\sqrt{5}-2\)

\(=-4\)

Học tốt 

Answer 2

\(\sqrt{49-12\sqrt{5}}-\sqrt{49+12\sqrt{5}}\)

\(=\sqrt{45-12\sqrt{5}+4}-\sqrt{45+12\sqrt{5}+4}\)

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

\(=|3\sqrt{5}-2|-|3\sqrt{5}+2|\)

\(=3\sqrt{5}-3\sqrt{5}-4=-4\)