(2x-y)(y+2x)-2(2y-x)(2y+x),其中x=1,y=3分之1

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(2x-y)(y+2x)-2(2y-x)(2y+x),其中x=1,y=3分之1

(2x-y)(y+2x)-2(2y-x)(2y+x),其中x=1,y=3分之1
(2x-y)(y+2x)-2(2y-x)(2y+x),其中x=1,y=3分之1

(2x-y)(y+2x)-2(2y-x)(2y+x),其中x=1,y=3分之1
(2x-y)(y+2x)-2(2y-x)(2y+x)
=(2x-y)(2x+y)-2(2y+x)(2y-x)
=4x^2-y^2-8y^2+2x^2
=6x^2-9y^2
=(2√3x+3y)(2√3x-3y)
∵x=1,y=1/3
∴原式＝(2√3-1)(2√3+1)
＝

注意楼上的错了

（2x-y)(y+2x)-(2y+x)(2y-x)
=(2x-y)(2x+y)-(2y+x)(2y-x)
=4x²-y²-(4y²-x²)
=4x²-y²-4y²+x²
=5x²-5y²
=5(x²-y²)...

全部展开

注意楼上的错了

（2x-y)(y+2x)-(2y+x)(2y-x)
=(2x-y)(2x+y)-(2y+x)(2y-x)
=4x²-y²-(4y²-x²)
=4x²-y²-4y²+x²
=5x²-5y²
=5(x²-y²)
=5*(1²-1/3²)
=5*8/9
=40/9

收起

=4x方-y方-2(4y方-x方)
=5x方-9y方
=5-1
=4

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