duytan1501
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cho a,b,c dương
chứng minh (1/a+1/b+1/c)(1/(a+1) +1/(b+1)+1/(c+1))>=9/(1+abc)
chứng minh (1/a+1/b+1/c)(1/(a+1) +1/(b+1)+1/(c+1))>=9/(1+abc)
Chứng minh:\[(\frac{1}{a}+\frac{1}{b}+\frac{1}{c})(\frac{1}{a+1}+\frac{1}{b+1}+\frac{1}{c+1})\ge \frac{9}{abc+1}\]cho a,b,c dương
chứng minh (1/a+1/b+1/c)(1/(a+1) +1/(b+1)+1/(c+1))>=9/(1+abc)