(a) The act of the majority of the directors present at a meeting at which a quorum is present shall be the act of the board of directors unless the act of a greater number is required by the articles of incorporation or the bylaws.
(b) Where the articles of incorporation or bylaws expressly permit such procedure, an action taken by a majority of the directors without a meeting in respect to any corporate matter is nevertheless a valid board action if either before or after the action is taken, all members of the board sign and file with the secretary for inclusion in the corporate minute book a memorandum showing the nature of the action taken, showing that each member of the board consented to the board acting informally in respect to the matter, and showing the names of the directors who approved the action taken and the names of those who opposed it.