[[a, -b*a, 0, 0], [-b*a, a, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]] * [[a, 0, 0, -b*a], [0, 1, 0, 0], [-b*a, 0, a, 0], [0, 0, 0, 1]]

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