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{(a - 4)/((a - 1) (a + 2)), 2/(a + 2), (3 a)/((a - 1) (a + 2))} /. a -> 0
{(a - 4)/((a - 1) (a + 2)), 2/(a + 2), (3 a)/((a - 1) (a + 2))} /. a -> 0
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