化简求值:3a²b-[2ab²-2(-a²b+4ab²)]-5ab²,其中a=-2,b=½
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![化简求值:3a²b-[2ab²-2(-a²b+4ab²)]-5ab²,其中a=-2,b=½](/uploads/image/z/1801747-19-7.jpg?t=%E5%8C%96%E7%AE%80%E6%B1%82%E5%80%BC%3A3a%26%23178%3Bb-%5B2ab%26%23178%3B-2%28-a%26%23178%3Bb%2B4ab%26%23178%3B%29%5D-5ab%26%23178%3B%2C%E5%85%B6%E4%B8%ADa%3D-2%2Cb%3D%26%23189%3B)
化简求值:3a²b-[2ab²-2(-a²b+4ab²)]-5ab²,其中a=-2,b=½
化简求值:3a²b-[2ab²-2(-a²b+4ab²)]-5ab²,其中a=-2,b=½
化简求值:3a²b-[2ab²-2(-a²b+4ab²)]-5ab²,其中a=-2,b=½
3a²b-[2ab²-2(-a²b+4ab²)]-5ab²
=3a²b-[2ab²+2a²b-8ab²]-5ab²
=3a²b-2ab²-2a²b+8ab²-5ab²
=3a²b-2a²b-2ab²+8ab²-5ab²
=a²b+ab²
=ab(a+b)
a=-2,b=½,
原式=-2*1/2*(-2+1/2)=-(-3/2)=3/2
3a²b-[2ab²-2(-a²b+4ab²)]-5ab²
=3a²b-[2ab²+2a²b-8ab²]-5ab²
=3a²b-2a²b+6ab²-5ab²
=a²b+ab²
当a=-2,b=½时
原式=(-2)²×½-2×(½)²=1.5
解
原式
=3a²b-(2ab²+2a²b-8ab²)-5ab²
=3a²b-(2a²b-6ab²)-5ab²
=(3a²b-2a²b)+(6ab²-5ab²)
=a²b+ab²
=ab(a+b)
=-2×(1/2)(-2+1/2)
=-(-3/2)
=3/2