有这样一道题,计算：（x-y)[(x+y)(x+y)-xy]-(x-y)[(x-y)(x-y)+xy]的值,其中x=2006,y=2007；某同学把“Y=

有这样一道题,计算：（x-y)[(x+y)(x+y)-xy]-(x-y)[(x-y)(x-y)+xy]的值,其中x=2006,y=2007；某同学把“Y=
有这样一道题,计算：（x-y)[(x+y)(x+y)-xy]-(x-y)[(x-y)(x-y)+xy]的值,其中x=2006,y=2007；某同学把“Y=

有这样一道题,计算：（x-y)[(x+y)(x+y)-xy]-(x-y)[(x-y)(x-y)+xy]的值,其中x=2006,y=2007；某同学把“Y=
原式=(x-y)(x²+2xy+y²-xy)-(x-y)(x²-2xy+y²+xy)
=(x-y)(x²+xy+y²)-(x+y)(x²-xy+y²)
=(x³-y³)-(x³+y³)
=-2y³
结果和x无关
所以不蹲x取何值,结果都不变

比是5:3
设长宽分别是5x和3x
所以(5x)2+(3x)2=(√68)2
25x2+9x2=68
x2=2
x=√2
所以长5√2，宽3√2
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