In: Advanced Math
A First Course in Abstract Algebra Chapter S.22, Problem 27E
Let F be a field of characteristic zero and let D be the formal polynomial differentiation map, so that. D(a0 + a1x + a2x^2 + ••• + anx^n) = a1 + 2 • a2x + •••+n• anxn-1, i.e.
F be a field of characteristic zero , D:F[x]→F[x].
C) Find the image of F[x] under D. Is it important which characteristic the field has? Can you explain this enough?
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is the polynomial differentiation map
Then, the image of under this map
is given by the set of polynomials
If
is a polynomial then
Therefore, the image consists of polynomials of the form
If the field has characteristic 2 for example, then the
polynomial
having the component
because characteristic 2 means
in this field
(definition of characteristic)
Thus, the image reduces to polynomials of the form
if the characteristic is 2 instead of 0. We can see that the
characteristic does play a role in defining the image of our
map
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