先化简,后求值:-2(mn-3m²)-【m²-5(mn-m²)+2mn】,其中m=1,n=-2.
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![先化简,后求值:-2(mn-3m²)-【m²-5(mn-m²)+2mn】,其中m=1,n=-2.](/uploads/image/z/336646-46-6.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%90%8E%E6%B1%82%E5%80%BC%3A-2%28mn-3m%26%23178%3B%29-%E3%80%90m%26%23178%3B-5%28mn-m%26%23178%3B%29%2B2mn%E3%80%91%2C%E5%85%B6%E4%B8%ADm%3D1%2Cn%3D-2.)
先化简,后求值:-2(mn-3m²)-【m²-5(mn-m²)+2mn】,其中m=1,n=-2.
先化简,后求值:-2(mn-3m²)-【m²-5(mn-m²)+2mn】,其中m=1,n=-2.
先化简,后求值:-2(mn-3m²)-【m²-5(mn-m²)+2mn】,其中m=1,n=-2.
原式=-2mn+6m²-m²+5(mn-m²)-2mn,
=-2mn+6m²-m²+5mn-5m²-2mn,
=mn,
当m=1,n=-2时,
原式=1×(-2)=-2.