1.(2x-3y)(2x+3y)=2.(5x+3y)(3y-5x)3.(x-3y)(-x+3y)=4.(x+y-z)²=

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1.(2x-3y)(2x+3y)=2.(5x+3y)(3y-5x)3.(x-3y)(-x+3y)=4.(x+y-z)²=
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1.(2x-3y)(2x+3y)=2.(5x+3y)(3y-5x)3.(x-3y)(-x+3y)=4.(x+y-z)²=
1.(2x-3y)(2x+3y)=
2.(5x+3y)(3y-5x)
3.(x-3y)(-x+3y)=
4.(x+y-z)²=

1.(2x-3y)(2x+3y)=2.(5x+3y)(3y-5x)3.(x-3y)(-x+3y)=4.(x+y-z)²=
1.(2x-3y)(2x+3y)=(2x)²-(3y)²=4x²-9y²
2.(5x+3y)(3y-5x)=(3y)²-(5x)²=9y²-25x²
3.(x-3y)(-x+3y)=-(x-3y)²=-x²+6xy-9y²
4.(x+y-z)²=[(x+y)-z]²
=(x+y)²-2(x+y)z+z²
=x²+2xy+y²-2xz-2yz+z²

1、=4x2-9y2
2、=9y2-25x2
3、=-x2+6xy-9y2
4、=x2+xy-xz+xy+y2-yz-xz-yz+z2=x2+y2+z2+2xy-2xz-2yz