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1 #exercise 2.A.17
- All polynomials have \((x+2)\) as a factor, and therefore can be written in the form \((x+2)f_j(x)\) where \(f_j(x)\) has degree at most \(m-1\).
- Because the \(z^0, z^1, ..., z^{m-1}\) is a spanning list of \(P_m-1(F)\), the spanning list of \(P_{m-1}(F)\) is of length \(m\).
- The original list had \(m+1\) elements, so by Axler 2.23 the list cannot be linearly independent.
- We can therefore find a non-trivial combination that equals zero, and can thus find a non-trivial combination of the original list by multiplying each vector by \((x-2)\).
2 Elementary Matrices
#incomplete
2.1 Things you can do
- Multiply a row by a nonzero scalar
- Add two rows
- Switch the ordering of the rows
The matrices that correspond to these operations are what we call #definition elementary matrices.
This includes the identity matrix (multiply by the scalar 1).