P/s: Các bạn giúp mình ý 4 câu hình với ạ..
4)2)
$VT=\sum \frac{a^{3}+b^{3}}{ab(a^{2}+b^{2})}=\sum \frac{(a+b)(a^{2}+b^{2})-ab(a+b)}{ab(a^{2}+b^{2})}=\sum \frac{a+b}{ab}-\sum \frac{a+b}{a^{2}+b^{2}}=2(\frac{1}{a}+\frac{1}{b}+\frac{1}{c})-(\sum \frac{a+b}{a^{2}+b^{2}})\geq 2(\frac{1}{a}+\frac{1}{b}+\frac{1}{c})-(\sum \frac{a+b}{2ab})=\frac{1}{a}+\frac{1}{b}+\frac{1}{c}$
Treasure every moment that you have!
And remember that Time waits for no one.
Yesterday is history. Tomorrow is a mystery.
Today is a gift. That’s why it’s called the present.
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