[if lt IE 7]> <body class="ie ie6 lte9 lte8 lte7 lang-en " > <![endif] [if IE 7]> <body class="ie ie7 lte9 lte8 lte7 lang-en " > <![endif] [if IE 8]> <body class="ie ie8 lte9 lte8 lang-en " > <![endif] [if IE 9]> <body class="ie ie9 lte9 lang-en " > <![endif] [if gt IE 9]> <body class="lang-en " > <![endif] [if !IE]><! <![endif] If you're seeing this message, it means we're having trouble loading external resources for Khan Academy. If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked. Skip to main content Khan Academy Subject: Computer programming Home Math Math K–8th K–2nd 3rd 4th 5th 6th 7th 8th Fundamentals Early math Arithmetic Pre-algebra Basic geometry High school and beyond Algebra basics Differential calculus Algebra I Integr...