先化简,再求值：当m等于2分之1时,求15m的平方 - 知识问答

先化简,再求值：当m等于2分之1时,求15m的平方-9-｛-4m的平方+｛5m-8m的平方（2m的平方-m）+9m的平方

2个回答

15m²-9-｛-4m²+｛5m-8m²（2m²-m）+9m²｝-3]
=15m²-9-[-4m²+(5m-16m^4+8m³+9m²)-3]
=15m²-9-(-4m²+5m-16m^4+8m³+9m²-3)
=15m²-9+4m²-5m+16m^4-8m³-9m²+3
=16m^4-8m³+10m²-5m-6
=16*(1/2)^4-8*(1/2)³+10*(1/2)²-5*(1/2)-6
=1-1+5/2-5/2-6
=-6

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