Áp BĐT Cô-si

1. Cho a,b,c \(\ge\) 0. Chứng minh các BĐT sau

a. \(\left(1+a\right)\left(1+b\right)\left(1+c\right)\ge\left(1+\sqrt[3]{abc}\right)^3\)

b. \(a^2\left(1+b^2\right)+b^2\left(1+c^2\right)+c^2\left(1+a^2\right)\ge6abc\)

c. \(\frac{ab}{a+b}+\frac{bc}{b+c}+\frac{c}{c+a}\le\frac{a+b+c}{2}\)

d. \(\frac{a}{b+c}+\frac{b}{c+a}+\frac{c}{a+b}\ge\frac{3}{2}\)

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