Every module over the integers has projective dimension at most one. This is the default strategy when the underlying ring is the integers, so in practice it never needs to be specified.
Our first example is the cokernel of a $3 \times 3$ matrix with positive small integer entries.
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The next example shows that the projective dimension can be less than one. In other words, a free module can have a non-trivial presentation.
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The final example involves a slightly larger matrix. The first matrix of the free resolution is the minimal presentation of the module.
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