Four typos

[kentemorrison]

One of these appears in the html but not the pdf. One is the opposite. Two appear in both versions.

Below Problem 123 (html): change "k/th" to "kth"

Problem 233 (pdf & html): capitalize "so" in last line

Problem 234 (pdf): change "generall" to "generally"

Theorem 3.1.5 (pdf & html): change (n+i-1)!/(n-1)! to (n+k-1)!/(n-1)!