先化简再求值：-2(mn-3m²)-[m²-5(mn-m²)+2mn],其中m=1 n=-2
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先化简再求值：-2(mn-3m²)-[m²-5(mn-m²)+2mn],其中m=1 n=-2
-2(mn-3m²)-[m²-5(mn-m²)+2mn]
=-2mn+6m²-m²+5mn-5m²-2mn
=mn
=1x-2
=-2
先化简再求值：-2(mn-3m²)-[m²-5(mn-m²)+2mn],其中m=1 n=-2
-2(mn-3m²)-[m²-5(mn-m²)+2mn]
=-2mn+6m²-m²+5mn-5m²-2mn
=mn
=1x-2
=-2