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Linear Algebra: Using Scalar Multiplication to prove that a set is within R2?

I'm studying for a linear algebra test, and I'm having a bit of trouble proving that a set is closed under Scalar Multiplication (I've got Vector Addition down fine).

Here's my example:

Show W = {(x, y) in R^2 : xy = | xy | } is closed under Scalar Multiplication.

I have this so far:

Let λ be a scalar.

Let the vector u = (u1, u2) in W, i.e. u1u2 = | u1u2 |

If you can help me figure out what's next, I will greatly appreciate it. Hopefully this will help me figure out subsequent problems. Thanks.

1 Answer

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  • 1 decade ago
    Favorite Answer

    closed under scalar multiplication simply means that if you multiply by a scalar (k) and you get an element of W then its closed in scalar multiplication...

    if u is an element of w

    ku is also an element means that w is closed under scalar multiplication

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