if a or b are above 1 we are done,.
so let us assume both < 1
by Bernoulli Inequality we have
(1+x)^n \>= 1+nx
so (1+\frac{a}{b})^{\frac{1}{a}} \ge 1+\frac{1}{b}
so (1+\frac{a}{b})^{\frac{1}{a}} > \frac{1}{b}
or 1+\frac{a}{b} > (\frac{1}{b})^a
or \frac{a+b}{b} > (\frac{1}{b})^a
or \frac{b}{a+b} < b^a
similarly
\frac{a}{a+b} < a^b
Adding, we get 1 < a^b + b^a
or a^b+b^a > 1
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