Fix typo in 9.1 (Patterns and flags)

9-regular-expressions/01-regexp-introduction/article.md

@@ -29,7 +29,7 @@ In both cases `regexp` becomes an instance of the built-in `RegExp` class.
 
 The main difference between these two syntaxes is that pattern using slashes `/.../` does not allow for expressions to be inserted (like string template literals with `${...}`). They are fully static.
 
-Slashes are used when we know the regular expression at the code writing time -- and that's the most common situation. While `new RegExp`, is more often used when we need to create a regexp "on the fly" from a dynamically generated string. For instance:
+Slashes are used when we know the regular expression at the code writing time -- and that's the most common situation. While `new RegExp` is more often used when we need to create a regexp "on the fly" from a dynamically generated string. For instance:
 
 ```js
 let tag = prompt("What tag do you want to find?", "h2");