[postlink]https://learn-pre-en.blogspot.com/2010/10/blog-post_23.html[/postlink]http://www.youtube.com/watch?v=U1RxBsJaMfQendofvid
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ฟังชั่น

[postlink]https://learn-pre-en.blogspot.com/2010/10/blog-post.html[/postlink]http://www.youtube.com/watch?v=13sIkGhlzVYendofvid
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แม่เหล็กไฟฟ้า