计算 12/ m²-9 + 2/3-m

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计算 12/ m²-9 + 2/3-m
计算 12/ m²-9 + 2/3-m

计算 12/ m²-9 + 2/3-m
解
12/(m²-9)+2/(3-m)
=12/(m-3)(m+3)-2(m+3)/(m-3)(m+3)
=(12-2m-6)/(m+3)(m-3)
=(-2m+6)/(m+3)(m-3)
=-2(m-3)/(m+3)(m-3)
=-2/(m+3)

原式=12/[(m+3)(m-3)] - 2/(m-3)
=[12-2(m+3)] / [(m+3)(m-3)]
=[6-2m]/[(m+3)(m-3)]
=(-2)/(m+3)
=-2/(m+3)

=12／(m+3)(m-3)-2(m+3)／(m+3)(m-3)
=(12-2m-6)／(m+3)(m-3)
=-2(m+3)／(m+3)(m-3)
=-2／(m-3)