问题补充:
先化简,再求值:若xy=-2,x+y=3,求代数式?(3xy+10y)+[5x-(2xy+2y-3x)]的值.
答案:
解:(3xy+10y)+[5x-(2xy+2y-3x)]
=3xy+10y+5x-2xy-2y+3x
=xy+8y+8x
=xy+8(x+y),
当xy=-2,x+y=3,原式=-2+8×3=22.
解析分析:首先根据整式的加减运算法则化简原式,然后将xy=-2,x+y=3代入即可求得
时间:2024-03-06 18:15:17
先化简,再求值:若xy=-2,x+y=3,求代数式?(3xy+10y)+[5x-(2xy+2y-3x)]的值.
解:(3xy+10y)+[5x-(2xy+2y-3x)]
=3xy+10y+5x-2xy-2y+3x
=xy+8y+8x
=xy+8(x+y),
当xy=-2,x+y=3,原式=-2+8×3=22.
解析分析:首先根据整式的加减运算法则化简原式,然后将xy=-2,x+y=3代入即可求得
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