x-y=4,xy=-2,求代数式〔2x+3y-2xy〕-〔x+4y+xy〕-〔3xy+2y-2x〕的值
来源:百度知道 编辑:UC知道 时间:2024/05/12 21:23:40
现在立刻马上就要
〔2x+3y-2xy〕-〔x+4y+xy〕-〔3xy+2y-2x〕
=2x+3y-2xy-x-4y-xy-3xy-2y+2x
=(2x-x+2x)+(3y-4y-2y)-(2xy+xy+3xy)
=3x-3y-6xy
=3(x-y)-6xy
=3*4-6*(-2)
=12-(-12)
=24
〔2x+3y-2xy〕-〔x+4y+xy〕-〔3xy+2y-2x〕
=2x+3y-2xy-x-4y-xy-3xy-2y+2x
=(2x-x+2x)+(3y-4y-2y)-(2xy+xy+3xy)
=3x-3y-6xy.
原式=2x+3y-2xy-x-4y-xy-3xy-2y+2x
=(2x-x+2x)+(3y-4y-2y)-(2xy+xy+3xy)
=3x-3y-6xy
=3(x-y+2xy)
把x-y=4 xy=-2代入
原式=24
〔2x+3y-2xy〕-〔x+4y+xy〕-〔3xy+2y-2x〕=3x-3y-6xy=3(x-y)-6xy=3*4-6*(-2)=12+12=24
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