Chứng minh rằng \(\frac{3}{2}\sqrt{6}+2\sqrt{\frac{2}{3}}-4\sqrt{\frac{3}{2}}=\frac{\sqrt{6}}{6}\)
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\(M=\sqrt{\frac{m}{1-2x+x^2}}\times\sqrt{\frac{4m-8mx+4mx^2}{81}}\)
\(=\frac{\sqrt{m}}{\sqrt{1-2x+x^2}}\times\frac{\sqrt{4m\times\left(1-2x+x^2\right)}}{\sqrt{81}}\)
\(=\frac{\sqrt{m}}{\sqrt{1-2x+x^2}}\times\frac{\sqrt{4m}\times\sqrt{1-2x+x^2}}{9}\)
\(=\frac{\sqrt{m}\times\sqrt{4m}}{9}\)
\(=\frac{2m}{9}\)
vậy . . .
\(M=\sqrt{\frac{m}{1-2x+x^2}}.\sqrt{\frac{4m-8mx+4mx^2}{81}}\)
\(=\sqrt{\frac{m}{\left(1-x\right)^2}}.\sqrt{\frac{4m\left(1-2x+x^2\right)}{81}}\)
\(=\sqrt{\frac{m}{\left(1-x\right)^2}.\frac{4m\left(1-x\right)^2}{81}}\)
\(=\frac{\sqrt{4m^2}}{81}\)
\(=\frac{\sqrt{4m^2}}{\sqrt{81}}=\frac{2m}{9}\)
Vậy : \(M=\frac{2m}{9}\)
Bài toán :
CMR : \(\frac{a}{b}+\sqrt{\frac{b}{c}}+\sqrt[3]{\frac{c}{a}}>\frac{5}{2}\forall a,b,c>0\)
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\(A=\frac{a}{b}+\sqrt{\frac{b}{c}}+\sqrt[3]{\frac{c}{a}}=\frac{a}{b}+\frac{1}{2}.\sqrt{\frac{b}{c}}+\frac{1}{2}\sqrt{\frac{b}{c}}+\frac{1}{3}\sqrt[3]{\frac{c}{a}}+\frac{1}{3}\sqrt[3]{\frac{c}{a}}+\frac{1}{3}\sqrt[3]{\frac{c}{a}}.\)
Áp dụng BĐT Cauchy cho 6 số dương
\(A\ge6\sqrt[6]{\frac{1}{2^2}.\frac{1}{3^3}.\frac{a}{b}.\sqrt{\frac{b}{c}}.\sqrt{\frac{b}{c}}.\sqrt[3]{\frac{c}{a}}.\sqrt[3]{\frac{c}{a}}.\sqrt[3]{\frac{c}{a}}}=6.\sqrt[6]{\frac{1}{108}}>6.\sqrt[6]{\frac{5^6}{12^6}}=\frac{6.5}{12}=\frac{5}{2}\)
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- Ngô Hồ Quỳnh Hân ko biết thì trả lời lm j??
mk cũng ko biết nha :)) > mk chỉ nhắc Ngô Hồ Quỳnh Hân thui :3
\(\frac{3}{2}\sqrt{6}+2\sqrt{\frac{2}{3}}-4\sqrt{\frac{3}{2}}=\frac{3}{2}\sqrt{6}+\frac{2.1}{3}\sqrt{2.3}-\frac{4.1}{2}\sqrt{3.2}\)
\(=\frac{3}{2}\sqrt{6}+\frac{2}{3}\sqrt{6}-2\sqrt{6}=\sqrt{6}\left(\frac{3}{2}+\frac{2}{3}-2\right)\)
\(=\sqrt{6}\left(\frac{9}{6}+\frac{4}{6}-\frac{12}{6}\right)=\sqrt{6}.\frac{1}{6}=\frac{\sqrt{6}}{6}\)
Vậy \(\frac{3}{2}\sqrt{6}+2\sqrt{\frac{2}{3}}-4\sqrt{\frac{3}{2}}=\frac{\sqrt{6}}{6}\)