chanel香奈儿历史:化简1/7(-2x+3y)(-2x-3y)-10(x+y)^2，x=1.25，y＝－0.25

来源：百度文库编辑：中科新闻网时间：2024/10/01 12:23:38

x=1.25,y=-0.25
所以x+y=1

1/7(-2x+3y)(-2x-3y)-10(x+y)^2
=1/7[(-2x)^2-(3y)^2]-10*1^2
=1/7(4x^2-9y^2)-10
=1/7[4*(5/4)^2-9*(-1/4)^2]-10
=1/7(25/4-9/16)-10
=(1/7)*(91/16)-10
=13/16-10
=-147/16

-6354/637

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