Answer
See the proof below.
Work Step by Step
$$\int_1^\infty x^{-2/3}dx=\lim\limits_{R \to \infty}\int_1^Rx^{-2/3}dx\\= \lim\limits_{R \to \infty}\frac{1}{1/3}x^{1/3}|_1^R=3\lim\limits_{R \to \infty}(R^{1/3}-1)\\=3(\infty-1)=\infty.$$