 \mathbf{I} - \mathbf{A})`,

where **I** is the `n`-by-`n` identity matrix. [2]_

References
----------
.. [1] M. Sullivan and M. Sullivan, III, "Algebra and Trigonometry,
   Enhanced With Graphing Utilities," Prentice-Hall, pg. 318, 1996.

.. [2] G. Strang, "Linear Algebra and Its Applications, 2nd Edition,"
   Academic Press, pg. 182, 1980.

Examples
--------
Given a sequence of a polynomial's zeros:

>>> import numpy as np

>>> np.poly((0, 0, 0)) # Multiple root example
array([1., 0., 0., 0.])

The line above represents z**3 + 0*z**2 + 0*z + 0.

>>> np.poly((-1./2, 0, 1./2))
array([ 1.  ,  0.  , -0.25,  0.  ])

The line above represents z**3 - z/4

>>> np.poly((np.random.random(1)[0], 0, np.random.random(1)[0]))
array([ 1.        , -0.77086955,  0.08618131,  0.        ]) # random

Given a square array object:

>>> P = np.array([[0, 1./3], [-1./2, 0]])
>>> np.poly(P)
array([1.        , 0.        , 0.16666667])

Note how in all cases the leading coefficient is always 1.

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