Exercise 7.4.8

Answers

If ϕ(T) is not injective, we can find a nonzero element x such that ϕ(T)(x) = 0. Hence the T-annihilator p(t) divides ϕ(t) by Exercise 7.3.15(b). This means p(t) = ϕ(t). If f(t) is the characteristic polynomial of T, then we have f(T)(x) = 0 by Cayley-Hamilton Theorem. Again by Exercise 7.3.15(b) we have ϕ(t) divides f(t).

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2011-06-27 00:00
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