fixed inject example and some minor edits

railties/guides/source/active_support_core_extensions.textile

@@ -1568,7 +1568,7 @@ The method +tableize+ is +underscore+ followed by +pluralize+.
 "InvoiceLine".tableize # => "invoice_lines"
 </ruby>
 
-As a rule of thumb, +tableize+ returns the table name that corresponds to a given model for simple cases. The actual implementation in Active Record is not straight +tableize+ indeed, because it also demodulizes de class name and checks a few options that may affect the returned string.
+As a rule of thumb, +tableize+ returns the table name that corresponds to a given model for simple cases. The actual implementation in Active Record is not straight +tableize+ indeed, because it also demodulizes the class name and checks a few options that may affect the returned string.
 
 NOTE: Defined in +active_support/core_ext/string/inflections.rb+.
 
@@ -1868,7 +1868,7 @@ The sum of an empty collection is zero by default, but this is customizable:
 [].sum(1) # => 1
 </ruby>
 
-If a block is given +sum+ becomes an iterator that yields the elements of the collection and sums the returned values:
+If a block is given, +sum+ becomes an iterator that yields the elements of the collection and sums the returned values:
 
 <ruby>
 (1..5).sum {|n| n * 2 } # => 30
@@ -1896,8 +1896,8 @@ h4. +each_with_object+
 The +inject+ method offers iteration with an accumulator:
 
 <ruby>
-[2, 3, 4].inject(1) {|acc, i| product*i } # => 24
-</ruby>
+[2, 3, 4].inject(1) {|product, i| product*i } # => 24
+</rubyproduct
 
 The block is expected to return the value for the accumulator in the next iteration, and this makes building mutable objects a bit cumbersome:
 
@@ -1942,7 +1942,7 @@ The method +many?+ is shorthand for +collection.size > 1+:
 <% end %>
 </erb>
 
-If an optional block is given +many?+ only takes into account those elements that return true:
+If an optional block is given, +many?+ only takes into account those elements that return true:
 
 <ruby>
 @see_more = videos.many? {|video| video.category == params[:category]}
@@ -1952,7 +1952,7 @@ NOTE: Defined in +active_support/core_ext/enumerable.rb+.
 
 h4. +exclude?+
 
-The predicate +exclude?+ tests whether a given object does *not* belong to the collection. It is the negation of the builtin +include?+:
+The predicate +exclude?+ tests whether a given object does *not* belong to the collection. It is the negation of the built-in +include?+:
 
 <ruby>
 to_visit << node if visited.exclude?(node)