先化简,再求值3(a²b+ab²)-5(a²b-4ab²),其中a=2,b=-1
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![先化简,再求值3(a²b+ab²)-5(a²b-4ab²),其中a=2,b=-1](/uploads/image/z/7176269-29-9.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%86%8D%E6%B1%82%E5%80%BC3%28a%26%23178%3Bb%2Bab%26%23178%3B%29-5%28a%26%23178%3Bb-4ab%26%23178%3B%29%2C%E5%85%B6%E4%B8%ADa%3D2%2Cb%3D-1)
先化简,再求值3(a²b+ab²)-5(a²b-4ab²),其中a=2,b=-1
先化简,再求值3(a²b+ab²)-5(a²b-4ab²),其中a=2,b=-1
先化简,再求值3(a²b+ab²)-5(a²b-4ab²),其中a=2,b=-1
3(a²b+ab²)-5(a²b-4ab²),
=3a²b+3ab²-5a²b+20ab²
=-2a²b+23ab²
将a=2,b=-1带入得:
原式=-2*4*(-1)+23*2*1=8+46=54
原式=3a²b+3ab²-5a²b+20ab²
=-2a²b+23ab²
=8+46
=54
3a²b+3ab²-5a²b+20ab²=
23ab²-2a²b=
ab(23b-2a)=
54