I'm not particularly strong in these types of questions and I never know where to begin.
Let $g(x) = 1/x$ for $1 ≤ x ≤ 3$ and let $\pi$ be the partition$ \{1, 2, 3 \} $ of $[1, 3]$. Find $m(π)$ and $M(π)$, the lower and upper sums for $g$ using $\pi$, respectively.
From what I know,
$m(π) = {\sum_1^n} (x_i-x_{i-1})\inf(g(x)|[x_{i-1},x_i])$
$M(π) = {\sum_1^n} (x_i-x_{i-1})\sup[g(x)|[x_{i-1},x_i])$
How do I go about working with these partitions to solve this?