Question 867004:  I have a Linear Algebra question.  
If Q is the vector space where f(x)=f^2(x) and f(x)=1 is Q a real vector space? 
Assuming it is a subspace of F(Negative Infinity to Infinity) we only need to check the 2 axioms addition and scalar multiplication 
1. Addition f(x) + f(x) = 1 + 1 = 2  
Here is my question: f(x) = 2 isn't within the space, does that mean we don't have a Real vector space?  
 
 Answer by jim_thompson5910(35256)      (Show Source): 
You can  put this solution on YOUR website! You are correct. 
 
 
 
According to this link, it says 
 
 
     "Closure: If u and v are any vectors in V, then the sum   u + v   belongs to V." 
 
 
Both f(x) = 1 and g(x) = 1 belong to the vector space Q, but h(x) = f(x) + g(x) = 2 does NOT belong to the vector space Q (since h^2(x) = 4, h(x) = 2, h^2(x) doesn't equal h(x))
 
 
So because the closure rule doesn't hold for all elements in Q, this means Q is NOT a vector space. 
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