Minkowski Inequality - Proof

Proof

First, we prove that f+g has finite p-norm if f and g both do, which follows by

Indeed, here we use the fact that is convex over (for greater than one) and so, by the definition of convexity,

This means that

Now, we can legitimately talk about . If it is zero, then Minkowski's inequality holds. We now assume that is not zero. Using Hölder's inequality

We obtain Minkowski's inequality by multiplying both sides by

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