Prove by cases that for all positive integers $n^n > n^{n-1}$
How am I going to make cases for this proposition? There are an infinite number of positive integers.
Prove by cases that for all positive integers $n^n > n^{n-1}$
How am I going to make cases for this proposition? There are an infinite number of positive integers.
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$$n^n > n^{n-1} = \frac{n^n}{n} \tag{*}$$
Well we know $n \ne 0$ so $(*)$ is equivalent to
$$1 > \frac{1}{n} \tag{**}$$
$(**)$ is true for $n > 1$
Therefore $(*)$ is true if $n > 1$
Both $(**)$ and $(*)$ do not hold for $n=1$