python - Numpy.linalg.det() returns incorrect result -

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would know why numpy returning "-2.0000000000000004" instead of "-2" 

>>> m = [[1,2],[3,4]] >>> numpy.linalg.det(m) -2.0000000000000004

i using python 3.4.2 (x64), numpy 1.9.1 , windows 7 x64.


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