Let $a$ and $b$ be real numbers such that $a > 0$ and $b > 0$. Prove that $(a + b) \left(\frac{1}{a} + \frac{1}{b}\right) \ge 4$ Similarly, prove that if $a$, $b$, and $c$ are positive real numbers, then $(a + b + c) \left(\frac{1}{a} + \frac{1}{b} + \frac{1}{c}\right) \ge 9$ Hint: use the theorem that $\frac{a}{b} + \frac{b}{a} \ge 2$.
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Step 1: Given that a > 0 and b > 0, we want to prove that a^2 + b^2 > 2ab. Show more…
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