已知x+y=-4,xy=3,求5(½ xy+2y)+〔6x-( 2xy+y-3x)〕的值
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已知x+y=-4,xy=3,求5(½ xy+2y)+〔6x-( 2xy+y-3x)〕的值
5(½ xy+2y)+〔6x-( 2xy+y-3x)〕
=2.5xy+10y+6x-2xy-y+3x
=½xy+9y+9x
=½×3+9×﹙-4﹚
=-34.5
再问: 若多项式2mx²-x平方+5x+8-(7x²-3y+5x)与x无关,求m²-[2m²-(5m-4)+4+m]的值
再答: 2mx²-x²+5x+8-(7x²-3y+5x) =﹙2m-1-7﹚x²+3y+8 多项式2mx²-x平方+5x+8-(7x²-3y+5x)与x无关 ∴2m-1-7=0 m=4 m²-[2m²-(5m-4)+4+m] =m²-[2m²-5m+4+4+m] =m²-2m²+4m-8 =-m²+4m-8 =-16+16-8 =-8
=2.5xy+10y+6x-2xy-y+3x
=½xy+9y+9x
=½×3+9×﹙-4﹚
=-34.5
再问: 若多项式2mx²-x平方+5x+8-(7x²-3y+5x)与x无关,求m²-[2m²-(5m-4)+4+m]的值
再答: 2mx²-x²+5x+8-(7x²-3y+5x) =﹙2m-1-7﹚x²+3y+8 多项式2mx²-x平方+5x+8-(7x²-3y+5x)与x无关 ∴2m-1-7=0 m=4 m²-[2m²-(5m-4)+4+m] =m²-[2m²-5m+4+4+m] =m²-2m²+4m-8 =-m²+4m-8 =-16+16-8 =-8
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