cài này toán 8 à ??
mình nghĩ giải vầy nè
Áp dụng BĐT Cauchy-Schwarz :
[tex]\frac{ac}{b}+\frac{ab}{c}\geq 2.\sqrt{\frac{ac}{b}.\frac{ab}{c}}=2.\sqrt{a^{2}}=2a[/tex]
[tex]\frac{ab}{c}+\frac{bc}{a}\geq \sqrt{\frac{ab}{c}.\frac{bc}{a}}=2.\sqrt{b^{2}}=2b[/tex]
[tex]\frac{ac}{b}+\frac{bc}{a}\geq 2\sqrt{\frac{ac}{b}+\frac{bc}{a}}=2.\sqrt{c^{2}}=2c[/tex] [tex]
=> (\frac{bc}{a}+\frac{ac}{b}+\frac{ab}{c})\geq 2(a+b+c)[/tex]
[tex]=>\frac{bc}{a}+\frac{ac}{b}+\frac{ab}{c}\geq a+b+c[/tex]