\(B=3\sqrt{2}-\sqrt{13+30\sqrt{2+\sqrt{\left(2\sqrt{2}+1\right)^2}}}\)
\(B=3\sqrt{2}-\sqrt{13+30\sqrt{2+2\sqrt{2}+1}}\)
\(B=3\sqrt{2}-\sqrt{13+30\sqrt{3+2\sqrt{2}}}\)
\(B=3\sqrt{2}-\sqrt{13+30\sqrt{\left(\sqrt{2}+1\right)^2}}\)
\(B=3\sqrt{2}-\sqrt{13+30\left(\sqrt{2+1}\right)}\)
\(B=3\sqrt{2}-\sqrt{13+30\sqrt{2}+30}\)
\(B=3\sqrt{2}-\sqrt{43+30\sqrt{2}}\)
\(B=3\sqrt{2}-\sqrt{\left(3\sqrt{2}+5\right)^2}\)
\(B=3\sqrt{2}-3\sqrt{2}-5\)
\(B=-5\)
vậy \(B=-5\)
\(B=3\sqrt{2}-\sqrt{13+30\sqrt{2+\sqrt{9+4\sqrt{2}}}}\\ \)
\(=3\sqrt{2}-\sqrt{13+30\sqrt{2+\sqrt{\left(2\sqrt{2}\right)^2+2.2\sqrt{2}+1^2}}}\)
\(=3\sqrt{2}-\sqrt{13+30\sqrt{2+2\sqrt{2}+1}}\)
\(=3\sqrt{2}-\sqrt{13+30\sqrt{\left(\sqrt{2}\right)^2+2\sqrt{2}+1}}\)
\(=3\sqrt{2}-\sqrt{13+30\left(\sqrt{2}+1\right)}\)
\(=3\sqrt{2}-\sqrt{13+30\sqrt{2}+30}\)
\(=3\sqrt{2}-\sqrt{43+30\sqrt{2}}\)
\(=3\sqrt{2}-\sqrt{\left(3\sqrt{2}\right)^2+2.5.3\sqrt{2}+5^2}\)
\(=3\sqrt{2}-3\sqrt{2}+5=5\)
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