Violympic toán 9
Các câu hỏi tương tự
11 tháng 2 2020 lúc 21:04
1. left{{}begin{matrix}a,b,c0a+b+c1end{matrix}right.. Cmr: frac{ab}{sqrt{left(1-cright)^2left(1+cright)}}+frac{bc}{sqrt{left(1-aright)^2left(1+aright)}}+frac{ca}{sqrt{left(1-bright)^3left(1+bright)}}lefrac{3sqrt{2}}{8}
2. left{{}begin{matrix}a,b,c0a+b+cle1end{matrix}right.. Cmr: frac{1}{a^2+b^2+c^2}+frac{1}{ableft(a+bright)}+frac{1}{bcleft(b+cright)}+frac{1}{acleft(a+cright)}gefrac{87}{2}
3. left{{}begin{matrix}a,b,c0ab+bc+ca2abcend{matrix}right.. Cmr: frac{1}{aleft(2a-1right)^2}+frac{1}{bleft...
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1. \(\left\{{}\begin{matrix}a,b,c>0\\a+b+c=1\end{matrix}\right.\). Cmr: \(\frac{ab}{\sqrt{\left(1-c\right)^2\left(1+c\right)}}+\frac{bc}{\sqrt{\left(1-a\right)^2\left(1+a\right)}}+\frac{ca}{\sqrt{\left(1-b\right)^3\left(1+b\right)}}\le\frac{3\sqrt{2}}{8}\)
2. \(\left\{{}\begin{matrix}a,b,c>0\\a+b+c\le1\end{matrix}\right.\). Cmr: \(\frac{1}{a^2+b^2+c^2}+\frac{1}{ab\left(a+b\right)}+\frac{1}{bc\left(b+c\right)}+\frac{1}{ac\left(a+c\right)}\ge\frac{87}{2}\)
3. \(\left\{{}\begin{matrix}a,b,c>0\\ab+bc+ca=2abc\end{matrix}\right.\). Cmr: \(\frac{1}{a\left(2a-1\right)^2}+\frac{1}{b\left(2b-1\right)^2}+\frac{1}{c\left(2c-1\right)^2}\ge\frac{1}{2}\)
4. \(\left\{{}\begin{matrix}x,y,z>0\\x+y+z=2015\end{matrix}\right.\). Tìm min \(A=\frac{x^4+y^4}{x^3+y^3}+\frac{y^4+z^4}{y^3+z^3}+\frac{z^4+x^4}{z^2+x^2}\)
Mn giúp mk với ạ! Thanks nhiều
28 tháng 10 2019 lúc 23:28
1. Cho a,b,c>0. Cmr: \(\frac{a}{\left(b+c\right)^2}+\frac{b}{\left(c+a\right)^2}+\frac{c}{\left(a+b\right)^2}\ge\frac{9}{4\left(a+b+c\right)}\)
19 tháng 10 2019 lúc 17:49
1. cho 0 ale ble c . Cmr: frac{2a^2}{b^2+c^2}+frac{2b^2}{c^2+a^2}+frac{2c^2}{a^2+b^2}lefrac{a^2}{b}+frac{b^2}{c}+frac{c^2}{a}
2. cho a,b,cge0. cmr: a^2+b^2+c^2+3sqrt[3]{left(abcright)^2}ge2left(ab+bc+caright)
3. a,b,c0. Cmr: sqrt{left(a^2b+b^2c+c^2aright)left(ab^2+bc^2+ca^2right)}ge abc+sqrt[3]{left(a^3+abcright)left(b^3+abcright)left(c^3+abcright)}
4. a,b,c0. Tìm Min Pleft(frac{a}{a+b}right)^4+left(frac{b}{b+c}right)^4+left(frac{c}{c+a}right)^4
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1. cho \(0< a\le b\le c\) . Cmr: \(\frac{2a^2}{b^2+c^2}+\frac{2b^2}{c^2+a^2}+\frac{2c^2}{a^2+b^2}\le\frac{a^2}{b}+\frac{b^2}{c}+\frac{c^2}{a}\)
2. cho \(a,b,c\ge0\). cmr: \(a^2+b^2+c^2+3\sqrt[3]{\left(abc\right)^2}\ge2\left(ab+bc+ca\right)\)
3. \(a,b,c>0.\) Cmr: \(\sqrt{\left(a^2b+b^2c+c^2a\right)\left(ab^2+bc^2+ca^2\right)}\ge abc+\sqrt[3]{\left(a^3+abc\right)\left(b^3+abc\right)\left(c^3+abc\right)}\)
4. \(a,b,c>0\). Tìm Min \(P=\left(\frac{a}{a+b}\right)^4+\left(\frac{b}{b+c}\right)^4+\left(\frac{c}{c+a}\right)^4\)
Cho a,b,c>0 thỏa mãn: a.b.c=8
Chứng minh: \(\frac{a^2}{\sqrt{\left(1+a^3\right).\left(1+b^3\right)}}+\frac{b^2}{\sqrt{\left(1+b^3\right).\left(1+c^3\right)}}+\frac{c^2}{\sqrt{\left(1+c^3\right).\left(1+a^3\right)}}\ge\frac{4}{3}\)
Cho các số dương a, b, c thỏa mãn ab+bc+ca=1.
CMR: \(\frac{1}{ab}+\frac{1}{bc}+\frac{1}{ca}\ge3+\sqrt{\frac{\left(a+b\right)\left(a+c\right)}{a^2}}+\sqrt{\frac{\left(b+c\right)\left(b+a\right)}{b^2}}+\sqrt{\frac{\left(c+a\right)\left(c+b\right)}{c^2}}\)
Cho a,b,c 0. CMR:
1. a^3+b^3+c^3ge3abc
2. frac{x^2}{a}+frac{y^2}{b}gefrac{left(x+yright)^2}{a+b}
3. frac{x^2}{a}+frac{y^2}{b}+frac{z^2}{c}gefrac{left(x+y+zright)^2}{a+b+c}
4. a^4+b^4+c^4ge abcleft(a+b+cright)
5. frac{1}{left(a+1right)^2}+frac{1}{left(b+1right)^2}gefrac{1}{ab+1}
6.frac{1}{1+a^3}+frac{1}{1+b^3}+frac{1}{1+c^3}gefrac{3}{1+abc}
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Cho a,b,c > 0. CMR:
1. \(a^3+b^3+c^3\ge3abc\)
2. \(\frac{x^2}{a}+\frac{y^2}{b}\ge\frac{\left(x+y\right)^2}{a+b}\)
3. \(\frac{x^2}{a}+\frac{y^2}{b}+\frac{z^2}{c}\ge\frac{\left(x+y+z\right)^2}{a+b+c}\)
4. \(a^4+b^4+c^4\ge abc\left(a+b+c\right)\)
5. \(\frac{1}{\left(a+1\right)^2}+\frac{1}{\left(b+1\right)^2}\ge\frac{1}{ab+1}\)
6.\(\frac{1}{1+a^3}+\frac{1}{1+b^3}+\frac{1}{1+c^3}\ge\frac{3}{1+abc}\)
Cho tam giác ABC có ABc, BCa, ACb và Pfrac{a+b+c}{2}
CMR: a) (P-a)(P-b)(P-c) lefrac{1}{8}abc
b) frac{1}{P-a}+frac{1}{P-b}+frac{1}{P-c}ge2left(frac{1}{a}+frac{1}{b}+frac{1}{c}right)
c) frac{1}{left(P-aright)^2}+frac{1}{left(P-bright)^2}+frac{1}{left(P-cright)^2}gefrac{P}{left(P-aright)left(P-bright)left(P-cright)}
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Cho tam giác ABC có AB=c, BC=a, AC=b và \(P=\frac{a+b+c}{2}\)
CMR: a) (P-a)(P-b)(P-c) \(\le\)\(\frac{1}{8}abc\)
b) \(\frac{1}{P-a}+\frac{1}{P-b}+\frac{1}{P-c}\ge2\left(\frac{1}{a}+\frac{1}{b}+\frac{1}{c}\right)\)
c) \(\frac{1}{\left(P-a\right)^2}+\frac{1}{\left(P-b\right)^2}+\frac{1}{\left(P-c\right)^2}\ge\frac{P}{\left(P-a\right)\left(P-b\right)\left(P-c\right)}\)
Cho các số thực dương a,b,c thỏa mãn a+b+c=3. Chứng minh \(\frac{1}{\left(a+b\right)^2}+\frac{1}{\left(b+c\right)^2}+\frac{1}{\left(c+a\right)^2}\ge\frac{3}{4}\)
a ) sqrt{frac{a^2}{b^2+left(c+aright)^2}}+sqrt{frac{b^2}{c^2+left(a+bright)^2}}+sqrt{frac{c^2}{a^2+left(b+cright)^2}}lefrac{3}{sqrt{5}}
với a,b,c là các số thực dương
b ) cho ba số thực dương a,b,c thỏa mãn abc1. tìm GTNN của biểu thức
Pfrac{left(1+aright)^2+b^2+5}{ab+a+4}+frac{left(1+bright)^2+c^2+5}{bc+b+4}+frac{left(1+cright)^2+a^2+5}{ca+c+4}
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a ) \(\sqrt{\frac{a^2}{b^2+\left(c+a\right)^2}}+\sqrt{\frac{b^2}{c^2+\left(a+b\right)^2}}+\sqrt{\frac{c^2}{a^2+\left(b+c\right)^2}}\le\frac{3}{\sqrt{5}}\)
với a,b,c là các số thực dương
b ) cho ba số thực dương a,b,c thỏa mãn abc=1. tìm GTNN của biểu thức
\(P=\frac{\left(1+a\right)^2+b^2+5}{ab+a+4}+\frac{\left(1+b\right)^2+c^2+5}{bc+b+4}+\frac{\left(1+c\right)^2+a^2+5}{ca+c+4}\)