cho a;b;c;d là các số thực dương thỏa mãn \(\frac{a}{1+a}+\frac{b}{1+b}+\frac{c}{1+c}+\frac{d}{1+d}\le1\)CMR:\(abcd\le\frac{1}{81}\)
Cho a,b,c,d>0 và \(\frac{1}{1+a}+\frac{1}{1+b}+\frac{1}{1+c}+\frac{1}{1+d}\ge3\)
Chứng minh rằng: \(a.b.c.d\le\frac{1}{81}\)
Cho \(0\le a,b,c\le1\)và a+b+c = 0. Chứng minh rằng \(\frac{1}{ab+1}+\frac{1}{bc+1}+\frac{1}{ac+1}\le\frac{5}{a+b+c}\)
cho số thực dương a,b,c,d. chứng minh:
\(\frac{1}{a^4+b^4+c^4+abcd}+\frac{1}{b^4+c^4+d^4+abcd}+\frac{1}{a^4+c^4+d^4+abcd}+\frac{1}{a^4+b^4+d^4+abcd}\le\frac{1}{abcd}\)
Cho a,b,c > 0 . Chứng minh :
\(\frac{1}{a^4+b^4+c^4+abcd}+\frac{1}{b^4+c^4+d^4+abcd}+\frac{1}{c^4+d^4+a^4+abcd}+\frac{1}{d^4+a^4+b^4+abcd}\le\frac{1}{abcd}\)
Cho \(\frac{1}{3}\le a,b,c\le1.\)Chứng minh rằng:
\(0,5\le\frac{a}{1+bc}+\frac{b}{1+ca}+\frac{c}{1+ab}\le1,9\)
Cho a,b,c,d>0 bt \(\frac{a}{1+a}+\frac{b}{1+b}+\frac{c}{1+c}+\frac{d}{1+d}\)<=1 CMR\(abcd\le\frac{1}{81}\)
Cho a,b,c,d>0 thỏa
\(\frac{1}{1+a}+\frac{1}{1+b}+\frac{1}{1+c}+\frac{1}{1+d}\ge3\)\
CMR: \(abcd\le\frac{1}{81}\)
cho a,b,c>0 và\(\frac{a}{1+a}+\frac{b}{1+b}+\frac{c}{1+c}\le1\)1
Chứng minh: \(abc\le\frac{1}{8}\)