Vector Spaces & Subspaces, Linear Algebra

kash25
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Homework Statement



Let V be a vector space and U a subspace of V . For a given x ∈ V , define T=
{x + u | u ∈ U }. Show that T is a subspace of V if and only if x ∈ U .


Homework Equations


Subspace Test:
1: The 0 vector of V is included in T.
2: T is closed under vector addition
3: T is closed under scalar multiplication


The Attempt at a Solution


I do not know how to show this...
 
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You're not trying very hard. Start with the forward direction. Show T is a subspace if x is in U. Try showing in this case T=U.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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