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Khan Academy
Matrices, vectors, vector spaces, transformations. Covers all topics in a first year college linear algebra course. This is an advanced course normally taken by science or engineering majors after taking at least two semesters of calculus (although calculus really isn't a prereq) so don't confuse this with regular high school algebra.Top Documentary Films - Watch Free Documentaries Online
Imagine a home that heats itself, that provides its own water, hat grows its own food. Imagine that it needs no expensive technology, that it recycles its own waste, that it has its own power source. And now imagine that it can be built anywhere, by anyone, out of the things society throws away.