(1).(x-2y)(x+2y)-(x+2y)^2(2).(2a+1)^2-(1-2a)^2(3).(3x-y)^2-(2x+y)^2+5x(y-x)

(1).(x-2y)(x+2y)-(x+2y)^2(2).(2a+1)^2-(1-2a)^2(3).(3x-y)^2-(2x+y)^2+5x(y-x)
(1).(x-2y)(x+2y)-(x+2y)^2
(2).(2a+1)^2-(1-2a)^2
(3).(3x-y)^2-(2x+y)^2+5x(y-x)

(1).(x-2y)(x+2y)-(x+2y)^2(2).(2a+1)^2-(1-2a)^2(3).(3x-y)^2-(2x+y)^2+5x(y-x)
(1).(x-2y)(x+2y)-(x+2y)^2
=[x^2-(2y)^2]-(x^2+4xy+4y^2)
=x^2-4y^2-x^2-4xy-4y^2
=-4xy-8y^2
(2).(2a+1)^2-(1-2a)^2
=[(2a+1)+(1-2a)][(2a+1)-(1-2a)]
=(2a+1+1-2a)(2a+1-1+2a)
=2*4a
=8a
(3).(3x-y)^2-(2x+y)^2+5x(y-x)
=[(3x-y)+(2x+y)][(3x-y)-(2x+y)]+5x(y-x)
=(3x-y+2x+y)(3x-y-2x-y)+5x(y-x)
=5x*(x-2y)+5x(y-x)
=5x(x-2y+y-x)
=5x(-y)
=-5xy

2.
2(2a+1-(1-2a))
=2*4a
=8a

(x+2y)(x-2y-x-2y)=(x+2y)(-4y)=-4xy-8xy;
(2a+1+1-2a)(2a+1-1+2a)=2(4a)=8a;
(3x-y+2x+y)(3x-y-2x-y)+5x(y-x)=5x(x-2y)+5x(y-x)=5x(y-x+x-2y)=-5xy

1、(x-2y-(x+2y))(x+2y)
=-4y(x+2y)

2(2a+1-(1-2a))
=2*4a
=8a
(x+2y)(x-2y-x-2y)=(x+2y)(-4y)=-4xy-8xy;
(2a+1+1-2a)(2a+1-1+2a)=2(4a)=8a;
(3x-y+2x+y)(3x-y-2x-y)+5x(y-x)=5x(x-2y)+5x(y-x)=5x(y-x+x-2y)=-5xy

1).(x-2y)(x+2y)-(x+2y)^2
=(x+2y)[(x-2y)-(x+2y)]（提取公因式）
=(x+2y)*(-4y)
=-4y(x+2y)
2).(2a+1)^2-(1-2a)^2 （平方差公式）
=(2a+1+1-2a)(2a+1-1+2a)
=2(4a)
=8a
3).(3x-y)^2-(2x+y)^2+5x(y-x) (先整理，再分解)
=9x^2-6xy+y^2-(4x^2+4xy+y^2)+5xy-5x^2
=-5xy

1、(x-2y-(x+2y))(x+2y)
=-4y(x+2y)

1、(x-2y-(x+2y))(x+2y)
=-4y(x+2y)
2.
2(2a+1-(1-2a))
=2*4a
=8a
3.(3x-y)^2-(2x+y)^2+5x(y-x)
=9x^2+y^2-6xy-(4x^+y^2+4xy)+5xy-5x^2
=(9-4-5)x^2+(1-1)y^2+(-6-4+5)xy
=-5xy

(x-2y)(x+2y)-(x+2y)²
=(x+2y)[(x-2y)-(x+2y)].........................<提取公因式>
=-4(x+2y)y
(2a+1)²-(1-2a)²
=[(2a+1)+(1-2a)][(2a+1)-(1-2a)]....................<平方差>
=8a

全部展开

(x-2y)(x+2y)-(x+2y)²
=(x+2y)[(x-2y)-(x+2y)].........................<提取公因式>
=-4(x+2y)y
(2a+1)²-(1-2a)²
=[(2a+1)+(1-2a)][(2a+1)-(1-2a)]....................<平方差>
=8a
(3x-y)²-(2x+y)²+5x(y-x)
=[(3x-y)+(2x+y)][(3x-y)-(2x+y)]+5x(y-x)............<平方差>
=5x(x-2y)+5x(y-x)
=5x[(x-2y)+(y-x)]..............................<提取公因式>
=-5xy

收起

(1).(x-2y)(x+2y)-(x+2y)^2
=x^2-(2y)^2-(x^2+4xy+4y^2)
=x^2-4y^2-x^2-4xy-4y^2
=-4xy;
(2).(2a+1)^2-(1-2a)^2
=[(2a+1)+(1-2a)][(2a+1)-(1-2a)]
=2*(4a)
=8a;
(3).(3x-y)^2-(2x+y)^2+5x(y-x)
=[(3x-y)+(2x+y)][(3x-y)-(2x+y)]+5xy-5x^2
=(5x)*(x-2y)+5xy-5x^2
=5x^2-10xy+5xy-5x^2
=-5xy.