Let f be an R-linear functional on X = R^2 defined

Let f be an R-linear functional on X = R^2 defined by f(x, y) = αx + βy, (x, y) ∈ X
for fixed α, β ∈ R \ {0} where X is equipped with the l^2-norm.
(1) Express ∥f∥_X∗ by α and β
(2) Find a 1-dimensional subspace L of X satisfying ∥f|L∥_L∗ = ∥f∥_X∗

No.1 回答者： ありものがたり 回答日時： 2020/06/10 16:29

So, what is your question on this problem?