- #1
1LastTry
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Homework Statement
Consider the vector space F(R) = {f | f : R → R}, with the standard operations. Recall that the zero of F(R) is the function that has the value 0 for all
x ∈ R:
Let U = {f ∈ F(R) | f(1) = f(−1)} be the subspace of functions which have
the same value at x = −1 and x = 1.
Define functions g; h; j and k ∈ F[R] by
g(x) = 2x^3− x − 2x^2+ 1;
h(x) = x^3+ x^2− x + 1;
k(x) = −x^3+ 5x^2+ x + 1 and
j(x) = x^3− x; ∀x ∈ R:
a) Show that g and h belong to U.
b) Show that k ∈ span{g; h}.
c) Show that j /∈ span{g; h}.
d) Show that span{g; h} /= span{g; h; j}.
Homework Equations
The Attempt at a Solution
My Attempt:
I have no idea how to do a) I tried plugging -1 and +1 in g and h however it doesn't meet the requirement of f(1)=f(-1).
I am sure I know how to do party b,c and d. However, I am doing something wrong and have no clue what it is...
So what I did for b) was:
k = a(g) + b(h)
after that you get something like (...)x^3 + (...)x^2 + (...)x + (a+b)
So I set the coefficient (...) equal to the coefficients of k (-1,5,1,1)
however I am unable to solve the linear system.
But it says it is in the span so I don't know what happened maybe mtah error, but I redid it a lot of times.